Symptoms of the disease are disorders of calcium metabolism. Adipose tissue in children
The formation of the bone skeleton, which, like a strong frame, holds the entire body, is a very long process. Its effectiveness depends on factors such as the functioning of internal organs, the content of certain chemicals in the blood and general condition child's body. And yet the most important condition for the normal and full development of bones is the proper functioning of phosphorus-calcium metabolism. Vitamin D is equally important for the formation of the skeleton.
Bones begin to form in fetal development in the first weeks of pregnancy, and by the end of the 15th week, the body of the unborn child and its bone apparatus are already fully formed. But this process continues long time until puberty at adolescence. Therefore, very important attention must be paid to sufficient intake of calcium, phosphorus and vitamin D already during pregnancy.
On the role of calcium in the body:
Calcium is an element that is present in sufficient quantities in the human body. Bones are 99% calcium. In addition, it is responsible for the normal functioning of nerves, muscles and is involved in the regulation of blood clotting. Calcium is also extremely important for the proper formation and growth of teeth in a child.
Calcium enters the body mainly with food - milk and dairy products.
Important! The daily requirement for calcium is:
In children from 0 to 6 months, 400 mg per day;
- In children infancy from 6 months to 1 year - 50 mg per 1 kg of body weight. So, a baby in the second half of life should receive about 600 mg of calcium per day. Please note that 100 ml of breast milk contains 30 mg of calcium, and 100 ml cow's milk- 120 mg of calcium;
- From 1 year to 10 years - 800 mg of calcium per day;
- Children aged 11 to 25 years - 1200 mg per day.
About the role of phosphorus:
Phosphorus makes up no more than 1% of the human body weight. About 85% of it is concentrated in the bones, and the rest in the muscles and tissues in the form of compounds. Foods rich in phosphorus are meat and milk. An extremely important element for the formation of musculoskeletal tissue and teeth.
Important! The daily requirement of children for phosphorus is:
From 0 to 1 month - 120 mg;
- From 1 to 6 months - 400 mg;
- From 7 to 12 months - 500 mg;
- From 1 to 3 years - 800 mg;
- From 4 to 7 years - 1450 mg.
It is important to understand that when breastfeeding The baby's need for phosphorus is fully satisfied with mother's milk.
Features of bone formation:
The absorption of phosphorus and calcium occurs in the intestine. The success and completeness of absorption depends on the normal functioning of the mucous membrane of the digestive system. Through the walls of the intestine, phosphorus and calcium are transported with the help of certain chemical compounds - vitamin D3 or parathyroid hormone produced by the parathyroid glands.
Important! First of all, diet is important to maintain normal levels of calcium and phosphorus in the body. The optimal ratio of calcium and phosphorus in the food consumed should be 2:1, respectively. That is, calcium should be supplied 2 times more than phosphorus.
It must be borne in mind that with a large amount of calcium, hypercalcemia may develop. This condition is dangerous because, against the background of an increase in the amount of calcium, an acute shortage of phosphorus develops, and calcification of internal organs occurs.
With an excess of phosphorus, hypocalcemia develops. On early dates such a disease, the body can cope on its own, but with a protracted course, there is a violation of bone mineralization and their curvature.
It greatly affects the formation of the bone skeleton and the process of assimilation of fats. As a result of diseases of the liver, pancreas, the likelihood of violations in the formation of the bone skeleton increases.
An important factor that interferes with the normal absorption of calcium is the so-called alkalization of the digestive tract. This phenomenon occurs when enveloping drugs, an excessive increase in the amount coli. Such disorders most often affect children who are artificially fed with mixtures based on cow's milk. This is easily explained by the fact that when feeding with a mixture, calcium enters the body in the form of insoluble salts and is excreted very quickly.
Phosphorus is absorbed much worse with increased acidity of the intestine, as well as with an excess of calcium and magnesium in the body.
Depot calcium and phosphorus:
After absorption, calcium and phosphorus are distributed throughout the body, including to the bones. There, calcium is deposited in two forms: easily removed and difficult to remove deposits. Of the easily soluble compounds, calcium easily returns back to the blood in case of hypocalcemia or increased acidity of fluids inside the body.
Important! Acidity blood develops with prolonged ailments of the child, for example, with diarrhea. This leads to a significant decrease in the content of calcium and phosphorus in the baby's bone tissue. Thanks to this process in the body, it is possible to normalize the pH level in a short time. Stocks of spent trace elements must be restored with baby food.
In babies suffering from chronic diseases, in which the pH level in the blood is significantly disturbed (diseases gastrointestinal tract, kidneys) develop very dangerous violations of this regulatory mechanism. As a result, there are serious violations phosphorus-calcium metabolism, which leads to a significant slowdown in the growth of the child due to excessive leaching of calcium and phosphorus from bone tissue.
The mechanism of excretion of phosphorus and calcium:
The final link of phosphorus-calcium metabolism in the body of a child is the kidneys. They filter vital elements from the blood, including calcium and phosphorus. They, depending on the needs of the body, either return to the blood or are excreted in the urine from the body.
Important! The factors that ensure the smooth operation of this system are a sufficient amount of vitamin D3 and parathyroid hormone, as well as the proper functioning of the kidneys. If one of these three factors is disturbed, a rather strong violation of the exchange of phosphorus and calcium develops.
In young children, the main manifestations of such disorders are softening occipital bones and excessive sweating.
About Vitamin D:
Under the influence of ultraviolet rays, 7-dehydrocholesterol contained in human skin is converted into its active form - cholecalciferol (in this case, a slight burn appears on the skin, which we refer to as sunburn). This is the best form of vitamin D3 for the body.
Important! It is impossible to artificially reproduce cholecalciferol. Taken as part of multivitamins or in monocomponent products, it is inactive and is mostly deposited in adipose and muscle tissues.
One part of vitamin D3 is metabolized in the liver and the excess is excreted in the bile or kidneys from the body. The other part is metabolized in the kidneys. It is this form that is active and has a direct effect on the organs that are involved in phosphorus-calcium metabolism. The renal metabolite of vitamin D3 is responsible for the proper absorption of calcium and phosphorus and other substances in the intestine and their fixation in bone tissue.
With an excess of vitamin D3, part of it is deposited in the muscles in an inactive form.
Important! With a significant increase in the content of vitamin D3 in the body, poisoning of the child develops. There are babies who experience signs of poisoning even with normal amounts of vitamin D3. This is due to their characteristics and predisposition. These children require less cholecalciferol.
Symptoms of a violation of phosphorus-calcium metabolism:
Regardless of the causes of such disorders in the initial stage, they are almost asymptomatic.
Symptoms of a violation of the metabolism of phosphorus and calcium in the body are as follows:
Increased perspiration in the occiput or other parts of the head. This is the very first sign that may indicate disorders in the metabolism of phosphorus and calcium. Thus, the body begins to more intensively remove chloride ions from the body both with urine and sweat, in order to compensate for the imbalance;
The back of the baby's head becomes flat and soft to the touch. If such symptoms are observed, then it is already safe to talk about the presence of a failure in the exchange of calcium and phosphorus in the baby's body;
Bone deformity. It develops, as a rule, if no measures have been taken to eliminate metabolic disorders;
Bone fractures. This is very serious and dangerous complication a disease that requires long-term or life-long treatment.
signs high content vitamin D3 in the body:
Strong thirst. Accordingly, the child very often asks for a potty or urinates on a diaper;
- Increased separation of urine;
- Lack of appetite;
- Increased anxiety of the baby;
- Sleep disorders;
- Regurgitation;
- Vomit;
- Decreased muscle tone;
- No increase in body weight;
- Hidden symptoms: calcification of the kidneys, kidney stones, high blood pressure.
Diagnostics:
It is very important that the doctor establishes as early as possible exact reason violations of phosphorus-calcium metabolism in a child. This will make it possible to prescribe timely and correct treatment.
When collecting an anamnesis, the doctor must ask the parents what the baby eats. If the child is breastfed, then the mother's diet is specified.
Next, it turns out if the baby has problems with the digestive tract, as this can lead to malabsorption of vital trace elements. As a result, the formation of bones in the baby will be disrupted.
In addition to the survey, the doctor prescribes a number of tests, among which the following are considered very informative:
fecal studies;
Smears for bacteriological research;
Urinalysis to detect excreted calcium from the body. For this analysis, urine is collected in the morning on an empty stomach. Based on the results of this analysis, the doctor concludes that there is hypercalciuria, which is associated with a very high content of vitamin D3 in the body;
Blood test, which consists in determining the level of calcium, phosphorus and alkaline phosphatase- an enzyme that indicates the growth of new cells in the baby's bone tissue). Thanks to this analysis, it is also possible to establish the correct functioning of the liver and kidneys;
Blood and urine tests to check for proper functioning pair thyroid gland;
Determination of the level of vitamin D3 and its metabolites. This analysis is optional. But it may be necessary if it is not possible to establish the cause of violations of phosphorus-calcium metabolism in the child's body. This analysis is very complex and requires state-of-the-art equipment.
Treatment:
Important! Never give your baby drops containing vitamin D3 at will, as its excess in the body is very dangerous. Any treatment should be prescribed only by a doctor after a preliminary examination.
The main directions of treatment of any disorder of calcium and phosphorus metabolism are as follows:
Proper diet. Depending on the problem, the doctor will recommend products that should be given preference, and which ones should be abandoned or limited;
- Calcium is found in large quantities in such foods: fresh vegetables (beets, celery, carrots, cucumbers), fruits and berries (currants, grapes, strawberries, strawberries, apricots, cherries, pineapples, oranges, peaches), nuts, meat, liver, seafood, dairy products.
Phosphorus is rich in foods such as cheese, cottage cheese, liver, meat, legumes, cauliflower, cucumbers, nuts, eggs, seafood
- Additional intake of vitamin D3 in the composition medicines(monocomponent or complex multivitamin) with an established deficiency;
- Additional intake of drugs containing daily or increased doses of calcium and phosphorus;
- Means for the treatment of pathologies that are the causes of violations of phosphorus-calcium metabolism in the baby's body.
Vitamin D3 Requirements:
Very important for small child has the amount of vitamin D that the mother received during pregnancy, especially in the third trimester.
Important! Full-term healthy babies mothers whose mothers took sufficient amounts of vitamin D, as a rule, do not require additional amounts from food.
Babies who are breastfed most often do not experience problems with calcium deficiency. After all, the calcium that is contained in breast milk is best absorbed in the body of a newborn baby.
Children who are fully or partially formula-fed receive additional vitamin D from formula milk. Its concentration in them, as a rule, is about 400 IU. That is, one liter of the mixture contains the daily requirement of vitamin D.
Vitamin D3, which is present in the skin of a child, covers the daily requirement by 30%. In those areas where there is a very large number of sunny days, such coverage is possible up to 100%.
Important! Be sure to monitor the amount of vitamin D3 that the baby receives from food. If there is a deficiency, be sure to compensate for it.
Important! The oral drops contain 300 IU of vitamin D3.
Take care of the health of your kids! They are your best!
Chapter V. Rickets, violation of phosphorus-calcium metabolism
rickets (R). Currently, R is understood as a violation of the mineralization of the growing bone, caused by a temporary mismatch between the needs of a growing organ ism in phosphates and calcium and the insufficiency of systems that ensure their delivery to the child's body. P is the most common disease associated with a violation of phosphorus-calcium homeostasis in children of the 1st year of life. P and hypovitaminosis D are ambiguous concepts!
IN International classification diseases of the 10th revision (ICD-10) R is included in the section of diseases of the endocrine system and metabolism (code E55.0). At the same time, the importance of hypovitaminosis D in its development is not denied.
The development of bone signs of P in young children is due to rapid growth rates, high speed of skeletal modeling and deficiency in the growing body of phosphates and calcium with imperfection of their transport, metabolism and utilization pathways (maturing heterochrony). Therefore, at present, P is referred to as borderline states.
Epidemiology. The frequency of P in children remains unexplored due to changes in ideas about the nature of this pathology. In the study of the level of calcitriol in children with clinic P, a decrease in the level of vitamin D in the blood was detected only in 7.5% of the examined children. According to modern authors, R occurs in young children with a frequency of 1.6 to 35%.
Factors contributing to the development of R:
1. High growth and development of children, increased need in mineral components (especially in premature babies);
2. Deficiency of calcium and phosphates in food;
3. Malabsorption of calcium and phosphates in the intestine, increased secretion them in the urine or impaired utilization of them in the bones;
4. Decrease in the level of calcium and blood phosphates with prolonged alkalosis, imbalance of zinc, magnesium, strontium, aluminum, due to various reasons;
5. Exogenous and endogenous vitamin D deficiency;
6. Reduced motor and support load;
7. Violation of the physiological ratio of osteotropic hormones - parathyroid hormone and calcitonin.
Etiology
Phosphorus-calcium metabolism in the body due to:
1. absorption of phosphorus and calcium in the intestine;
2. their interchange between blood and bone tissue;
3. release of calcium and phosphorus from the body - reabsorption in the renal tubules.
All factors leading to impaired calcium metabolism are partially compensated by the leaching of calcium from the bones into the blood, which leads to the development of osteomalacia or osteoporosis.
The daily requirement for calcium in infants is 50 mg per 1 kg of weight. Dairy products are the most important source of calcium. Calcium absorption in the intestine depends not only on its amount in food, but also on its solubility, ratio with phosphorus (optimum 2: 1), the presence of bile salts, the pH level (the more pronounced alkaline reaction the worse the absorption). Vitamin D is the main regulator of calcium absorption.
The bulk (more than 90%) of calcium and 70% of phosphorus is in the bones in the form of inorganic salts. Throughout life, bone tissue is in ongoing process creation and destruction due to the interaction of three types of cells: osteoblasts, osteocytes and osteoclasts. Bones are actively involved in the regulation of calcium and phosphorus metabolism, maintaining their stable level in the blood. With a decrease in the level of calcium and phosphorus in the blood (the product of Ca × P is a constant value and equal to 4.5-5.0), bone resorption develops due to the activation of the action of osteoclasts, which increases the flow of these ions into the blood; with an increase given coefficient there is an excessive deposition of salts in the bone.
The excretion of calcium and phosphorus by the kidneys is parallel to their content in the blood. With a normal calcium content, its excretion in the urine is insignificant, with hypocalcemia this amount decreases sharply, hypercalcemia increases the calcium content in the urine.
The main regulators of phosphorus-calcium metabolism, along with vitamin D are parathyroid hormone (PG) and calcitonin (CT)- thyroid hormone.
The name "vitamin D" means a group of substances (about 10) contained in products of plant and animal origin, which have an effect on calcium-phosphorus metabolism. The most active of them are ergocalciferol (vitamin D 2) and cholecalciferol (vitamin D 3). Ergocalciferol is found in small amounts in vegetable oil, wheat germ; cholecalciferol - in fish oil, milk, butter, eggs. Physiological daily requirement in vitamin D, the value is quite stable and amounts to 400-500 IU. During pregnancy and breastfeeding, it increases by 1.5, maximum 2 times.
Rice. 1.19.The scheme of regulation of phosphorus-calcium metabolism in the body
The normal provision of the body with vitamin D is associated not only with its intake with food, but also with the formation in the skin under the influence of UV rays. At the same time, ergocalciferol is formed from ergosterol (the precursor of vitamin D 2), and cholecalciferol is formed from 7-dehydrocholesterol (the precursor of vitamin D 3).
Rice. 1.20.Biotransformation of vitamin D
With sufficient insolation (a 10-minute irradiation of the hands is enough), the skin synthesizes the amount of vitamin D necessary for the body. With insufficient natural insolation: climatic and geographical features, living conditions ( countryside or an industrial city), household factors, season, etc. the missing amount of vitamin D must come from food or in the form of drugs. In pregnant women, vitamin D is deposited in the placenta, which provides the newborn with anti-rachitic substances for some time after birth.
Vitamins D 2 and D 3 have very little biological activity. The physiological effect on target organs (intestines, bones, kidneys) is carried out by their metabolites formed in the liver and kidneys as a result of enzymatic hydroxylation. In the liver, under the influence of hydroxylase, 25-hydroxycholecalciferol 25(OH)D 3 -calcidierol is formed. In the kidneys, as a result of another hydroxylation, dihydroxycholecalciferol is synthesized - 1,25-(OH) 2 D 3 -calcitrierol, which is the most active metabolite of vitamin D. In addition to these two main metabolites, other vitamin D 3 compounds are synthesized in the body - 24.25 (OH) 2 D 3 , 25.26 (OH) 2 D 3 , 21.25 (OH) 2 D 3 , the action of which has not been studied enough.
Main physiological function vitamin D (i.e. its active metabolites) in the body - regulation and maintenance of the phosphorus-calcium homeostasis of the body at the required level. This is ensured by its effect on the absorption of calcium in the intestines, on the deposition of its salts in the bones (bone mineralization) and on the reabsorption of calcium and phosphorus in the renal tubules.
The mechanism of calcium absorption in the intestine is associated with the synthesis of calcium-binding protein (BCP) by enterocytes. CSC synthesis is induced by calcitriol through the genetic apparatus of cells, i.e. according to the mechanism of action, 1,25 (OH) 2 D 3 is similar to hormones.
In conditions of hypocalcemia, vitamin D temporarily increases bone resorption, enhances calcium absorption in the intestine and its reabsorption in the kidneys, thereby increasing the level of calcium in the blood. With normocalcemia, it activates the activity of osteoblasts, reduces bone resorption and its cortical porosity.
IN last years it has been shown that the cells of many organs have receptors for calcitriol, which thereby participates in the universal regulation of intracellular enzyme systems. Activation of the corresponding receptors through adenylate cyclase and cAMP mobilizes calcium and its association with the calmodulin protein, which promotes signal transmission and enhances the function of the cell, and, accordingly, of the entire organ.
Vitamin D stimulates the pyruvate-citrate reaction in the Krebs cycle, has an immunomodulatory effect, regulates the level of pituitary thyroid-stimulating hormone secretion, directly or indirectly (through calcium) affects the production of insulin by the pancreas.
The second most important regulator of phosphorus-calcium metabolism is parathyroid hormone (PG). The production of this hormone by the parathyroid glands increases in the presence of hypocalcemia, and, especially, with a decrease in the concentration of ionized calcium in plasma and extracellular fluid. The main target organs for parathyroid hormone are the kidneys, bones and, to a lesser extent, the gastrointestinal tract.
The action of parathyroid hormone on the kidneys is manifested by an increase in the reabsorption of calcium and magnesium. At the same time, phosphorus reabsorption decreases, which leads to hyperphosphaturia and hypophosphatemia. It is also believed that parathyroid hormone increases the ability of the kidneys to form calcitriol, thereby enhancing the absorption of calcium in the intestine.
In the bone tissue, under the influence of parathyroid hormone, calcium of bone apatites passes into a soluble form, due to which it is mobilized and released into the blood, which is accompanied by the development of osteomalacia and even osteoporosis. Thus, parathyroid hormone is the main calcium-sparing hormone. It carries out rapid regulation of calcium homeostasis, constant regulation of calcium metabolism is a function of vitamin D and its metabolites. The formation of PG is stimulated by hypocalcemia, with high level calcium in the blood, its production decreases.
The third regulator of calcium metabolism is calcitonin (CT)- a hormone produced by C-cells of the parafollicular apparatus of the thyroid gland. By its action on calcium homeostasis, it is a parathyroid hormone antagonist. Its secretion increases with an increase in the level of calcium in the blood and decreases with a decrease. A diet high in calcium also stimulates the secretion of calcitonin. This effect is mediated by glucagon, which is thus a biochemical activator of CT production. Calcitonin protects the body from hypercalcemic conditions, reduces the number and activity of osteoclasts, reducing bone resorption, enhances calcium deposition in bones, preventing the development of osteomalacia and osteoporosis, and activates its excretion in the urine. The possibility of an inhibitory effect of CT on the formation of calcitriol in the kidneys is assumed.
Phosphorus-calcium homeostasis, in addition to the three above described (vitamin D, parathyroid hormone, calcitonin), is influenced by many other factors. Trace elements Mg, Al are calcium competitors in the process of absorption; Ba, Pb, Sr and Si can replace it in salts found in bone tissue; thyroid hormones, growth hormone, androgens activate the deposition of calcium in the bones, reduce its content in the blood, glucocorticoids contribute to the development of osteoporosis and leaching of calcium into the blood; vitamin A is an antagonist of vitamin D in the process of absorption in the intestine. However Negative influence These and many other factors on phosphorus-calcium homeostasis is manifested, as a rule, with significant deviations in the content of these substances in the body. The regulation of phosphorus-calcium metabolism in the body is shown in Figure 1.19.
Pathogenesis
The main mechanisms of P pathogenesis are:
1. Malabsorption of calcium and phosphates in the intestines, increased excretion of them in the urine or impaired utilization of them in the bones.
2. Decrease in the level of calcium and phosphates in the blood and impaired bone mineralization. This is facilitated by: prolonged alkalosis, deficiency of zinc, magnesium, strontium, aluminum.
3. Violation of the physiological ratio of osteotropic hormones - parathyroid hormone and calcitonin.
4. Exo- and endogenous vitamin D deficiency, as well as more low level vitamin D metabolite. This is facilitated by: diseases of the kidneys, liver, intestines, nutritional deficiencies.
Violations of phosphorus-calcium metabolism in young children are most often manifested by hypocalcemia various origins with clinical manifestations of the musculoskeletal system. The most common disease is R. The cause of hypocalcemia may be a deficiency of vitamin D and disorders of its metabolism, due to the temporary immaturity of the enzyme systems of organs (kidneys, liver) that regulate this process. Less common are primary genetically determined diseases of the kidneys, gastrointestinal tract, parathyroid glands, and the skeletal system, accompanied by disturbances in phosphorus-calcium homeostasis with a similar clinical picture.
Classification(see table 1.40).
Tab. 1.40.Rickets classification
Research: general analysis blood and urine, blood alkaline phosphatase, blood calcium and phosphorus, bone radiography.
Clinic. It is currently believed that children with Р I degree only the presence of bone changes is mandatory. THAT. the neurological changes previously described for this severity of rickets do not apply to P.
For R II degree pronounced changes in the bones are characteristic: frontal and parietal tubercles, rosaries, deformity of the chest, often varus deformity of the extremities. Radiologically, there is an expansion of the metaphyses of the tubular bones, their cup-shaped deformation.
For R III degree characterized by gross deformities of the skull, chest, lower extremities, delayed development of static functions. In addition, are determined: shortness of breath, tachycardia, liver enlargement.
Initial signs P- softening of the edges of a large fontanel, craniotabes. The question of the so-called initial signs R in the form of sweating, restlessness, startling, etc. has not been completely resolved.
peak period- signs of bone osteomalacia or osteoid hyperplasia, osteoporosis. The most pronounced clinical and radiological changes coincide with severe hypophosphatemia.
convalescence period – reverse development clinics R. An x-ray examination shows a clear line of calcification in the metaphyseal zone, the level of phosphates normalizes, a slight hypocalcemia persists, and a moderate increase in the level of alkaline phosphatase.
Current R– sharp and subacute At acute course manifestations of osteomalacia predominate, and with subacute course- osteoid hyperplasia. Manifestations of osteomalacia are: softening of the edges of the large fontanel, craniotabes, rachitic kyphosis, curvature of the limbs, rachitic deformity of the chest.
The signs of osteoid hyperplasia include: rachitic rosary, frontal and occipital tubercles, "strings of pearls", etc.
Diagnosis. On an outpatient basis, clinical manifestations are sufficient to make a diagnosis of P.
Laboratory confirmation of P I degree- slight hypophosphatemia and increased activity of alkaline phosphatase.
Laboratory confirmation of P II degree– decrease in the level of phosphates, calcium, increased activity of alkaline phosphatase.
Laboratory confirmation of P III degree- X-ray examination shows a rough restructuring of the pattern and development of bones, expansion and blurring of the metaphyseal zone, fractures or displacements are possible. In the blood, a pronounced decrease in the levels of phosphates and calcium, an increase in the level of alkaline phosphatase are determined.
The only reliable sign of the diagnosis of P is a decrease in the level of vitamin D in the blood (determination of the level of 25-OH-D 3).
Differential Diagnosis R is carried out with: D-resistant forms of rickets, D-dependent forms of rickets I and II types, phosphate diabetes, de Toni-Debre-Fanconi syndrome, renal tubular acidosis, osteoporosis.
Tab. 1.41.Differential diagnosis of rickets
| signs | Vitamin D-deficient rickets | Phosphate diabetes | Renal tubular acidosis | De Toni-Debre-Fanconi disease |
| Inheritance type | No | Dominant. X-linked | Possibly autosomal recessive or autosomal dominant | autosomal recessive or autosomal dominant |
| Dates of manifestation | 1.5-3 months | Over 1 year old | 6 months-2 years | Over 1-2 years old |
| First clinical manifestations | Damage to the skeletal system | Severe deformity of the lower extremities, bracelets, hypotension, | Polyuria, polydipsia, tearfulness, muscle pain, hypotension | Unexplained fever, polyuria, polydipsia, muscle pain |
| Specific features | Craniotabes, frontal and occipital protuberances, bracelets, limb deformity | Progressive varus deformity of the extremities | Polyuria, polydipsia, hypotension to atony, adynamia, liver enlargement, constipation, hallux valgus shins | Fever, progressive multiple bone deformities, liver enlargement, decreased blood pressure, constipation |
| Physical development | Without features | Growth deficit at normal weight | Decreased height and weight | Decreased height and weight |
| blood calcium | lowered | Norm | Norm | More often the norm |
| Phosphorus | lowered | Dramatically reduced | lowered | Dramatically reduced |
| Potassium | norm | norm | lowered | lowered |
| Sodium | Norm | norm | lowered | lowered |
| KOS | More often acidosis | metabolic acidosis | Severe metabolic acidosis | |
| Aminoaciduria | There is | norm | norm | expressed |
| Phosphaturia | There is | pronounced | moderate | pronounced |
| Calciuria | lowered | norm | significant | significant |
| X-ray of the bones of the skeleton | Goblet expansions of the metaphyses | Rough goblet expansions of the metaphyses, thickening of the cortical layer of the periosteum | Acute systemic osteoporosis. Blurred contours of the metaphyses, concentric bone atrophy | Osteoporosis, trabecular striation in the distal and proximal diaphyses |
| The effect of vitamin D treatment | good effect | Minor | Satisfactory effect at high doses |
Osteoporosis- a decrease in bone mass and a violation of the structure of bone tissue - can be associated not only with P, but also with other factors. The causes of osteoporosis are: endocrine-metabolic disorders; malnutrition and digestion; the use of a number of drugs (hormones, anticonvulsants, antacids, heparin); genetic factors (imperfect osteogenesis, Marfan's syndrome, homocystinuria); prolonged immobilization; malignant tumors; chronic renal failure. In these cases, the diagnosis of P is invalid, despite the clinical similarity.
Treatment. Treatment goals: restoration of vitamin D deficiency in the body, correction of phosphorus-calcium metabolism disorders, relief of manifestations of P (deformation of bones, muscular hypotension dysfunction of internal organs).
The scheme of treatment.Mandatory activities: vitamin D preparations, regimen, solar and air procedures.
Auxiliary treatment: diet, vitamin therapy, water procedures, massage calcium preparations.
the need for an in-depth examination (conducting a differential diagnosis), the lack of effect from the appointment of vitamin D preparations.
Mode, appropriate for the age of the child, prolonged exposure to the air with sufficient insolation (at least 2-3 hours daily).
Diet - natural feeding, with artificial feeding, the use of adapted mixtures corresponding to the age of the child. The timely introduction of complementary foods is important.
Tab.1. 42. Vitamin D medicines
| Name of the drug | Vitamin D content |
| Aquadetrim Vitamin D 3, Aqueous solution | 1 ml - 30 drops; 1 drop - 500 IU |
| Videhol, oil solution D 3 , 0.125% | 1 drop 500 IU |
| Videhol, oily solution, 0.25% | 1 drop -1000 IU |
| Ergocalciferol solution (vitamin D 2) oil solution, 0.0625% | 1 drop - 625 IU |
| Solution of ergocalciferol (vitamin D 2) in oil in capsules | 1 capsule - 500 IU |
| Dragee ergocalciferol (vitamin D 2) | 1 dragee - 500 IU |
| Ergocalciferol solution (vitamin D 2 in oil, 0.125% | 1 drop - 1250 IU |
| Ergocalciferol solution (vitamin D 2 in oil, 0.5% | 1 drop - 5000 IU |
| Oxidevit (calcitriol, 1,25(OH)2D 2 | 1 capsule - 1 mcg 0.00025 mg |
| Fish oil capsules (Norway), Meller | 1 capsule - 52 IU |
Nearly all pediatricians now agree that specific treatment It is advisable to carry out R with small therapeutic doses of vitamin D. The daily dose of vitamin D at I-II degree P while it is 1500-2000 IU, the course is 100,000-150,000 IU; at II-III degree - 3000-4000 IU, course 200000-400000 IU. This treatment is carried out during the peak period, confirmed by biochemical data (decrease in blood calcium and phosphorus, increase in alkaline phosphatase). At the end of the course, if necessary, it is advisable to switch to a prophylactic (physiological) dose of vitamin D. Recommended in the past shock, semi-shock methods, repeated treatment courses currently not in use. When carrying out specific therapy, it is necessary to monitor the level of calcium in the blood by regular (1 time in 10-14 days) setting the Sulkovich reaction (degree of calciuria).
Tab. 1.43. Modern calcium-containing preparations
| Name | Ca content | Manufacturer country |
| Preparations containing calcium carbonate | ||
| UPSAVIT calcium | France | |
| Additive calcium | Poland | |
| Calcium-D 3 -Nycomed | 1250+D 3 200 units | Norway |
| Vitrum calcium | 1250+D 3 200 units | USA |
| Ideos | 1250+D 3,400 units | France |
| Vitacalcin | Slovakia | |
| Osteokea | Great Britain | |
| Ca-sandos forte | Switzerland | |
| Complex preparations | ||
| Osteogenon | Ca 178, P 82, growth factors | France |
| Vitrum osteomag | Ca, Mg, Zn, Cu, D 3 | USA |
| Berocca Ca and Mg | Ca, Mg and vitamins | Switzerland |
| Calcium SEDICO | Ca, D 3 , vit. WITH | Egypt |
| Kaltsinova | Ca, P, vit. D, A, C, B 6 | Slovenia |
Calcium preparations are indicated for premature babies, breastfed children, in courses of 2-3 weeks. The dose is selected depending on the age, severity of R and the degree of metabolic disorders.
It is advisable to combine vitamin D preparations with vitamins of group B (B 1, B 2, B 6), C, A, E.
To reduce the severity autonomic disorders shows the use of potassium and magnesium preparations (panangin, asparkam) at the rate of 10 mg / kg / day for 3-4 weeks.
Prevention. At present, non-specific antenatal prophylaxis of P is to create a pregnant woman optimal conditions for the growth and development of the fetus: rational nutrition with sufficient intake of not only proteins, fats, carbohydrates, but also micro and macro elements (including calcium and phosphorus), vitamins (including vitamin D); the prohibition of a pregnant woman to take toxic (especially for the fetus) substances - tobacco, alcohol, drugs; exclusion of the possibility of contact of a pregnant woman with others toxic substances- chemicals, drugs, pesticides, etc. A pregnant woman should lead a physically active lifestyle, as much as possible (at least 4-5 hours a day) be on fresh air, observe the regime of the day with sufficient rest day and night. In this case, there is no need to additionally prescribe vitamin D to the pregnant woman.
Antenatal specific prophylaxis of P by prescribing 200-400 IU of vitamin D per day from the 32nd week of pregnancy for 8 weeks (perform only in the winter or spring period of the year). For pregnant women at risk, specific P prophylaxis is carried out regardless of the season of the year.
Postnatal non-specific prevention of P includes: breastfeeding; timely introduction of complementary foods (it is better to start with vegetable puree), juices; daily stay in the fresh air, free swaddling, massage, gymnastics, light-air and hygienic baths.
The physiological need of a child for vitamin D is 200 IU per day.
Postnatal specific prophylaxis of P is carried out for children only in the period of late autumn - early spring at a dose of 400 IU per day, starting from 4 weeks of age. Additional administration of vitamin D in the 2nd year of life is not advisable. The mixtures used for artificial feeding contain all the necessary vitamins and minerals in physiological doses, and therefore there is no need for additional vitamin D. For children with small fontanelles, it is preferable to use non-specific methods prevention R.
For preterm infants, the issue of prophylactic administration of vitamin D should only be considered after optimizing dietary intake of calcium and phosphorus. It has been established that hypovitaminosis D is practically not detected in premature infants. In the development of osteopenia in them crucial is deficient in calcium and phosphate. It is traditionally considered that the prophylactic dose of vitamin D for premature babies is 400-1000 IU per day.
SPASMOPHILIA (C)- a peculiar condition of young children with signs of rickets, caused by a violation of mineral metabolism, hypofunction of the parathyroid glands, manifested by signs of increased neuromuscular excitability and a tendency to convulsions.
Epidemiology. C occurs almost exclusively in children in the first 2 years of age, in about 3.5-4% of all children.
Pathogenesis. Violations of mineral metabolism in C are more pronounced than in rickets and are characterized by some features. Indicators of metabolic changes are hypocalcemia, severe hypophosphatemia, hypomagnesemia, hyponatremia, hypochloremia, hyperkalemia and alkalosis. Calcium deficiency develops due to a decrease in the content of free and bound calcium. Main metabolic disorders at C are hypocalcemia and alkalosis, which are explained by a decrease in the function of the parathyroid glands. The main clinical manifestations of C (spasms and convulsions) are explained by a sharp lack of calcium and the resulting increased excitability of the nerves. Additional factors contributing to the occurrence of seizures are considered to be a lack of sodium and chlorine, as well as a pronounced lack of magnesium and an increased concentration of potassium (because sodium reduces the excitability of the neuromuscular system). The occurrence of seizures can also be explained by a lack of vitamin B 1, which is present in C. With its pronounced deficiency, sharp disturbances occur in the glycolytic chain with the formation of pyruvic acid, which plays an important role in the occurrence of seizures.
C occurs in all seasons of the year, but more often develops in the spring.
An attack of C can be provoked by the development of any disease with a high temperature, frequent vomiting with gastrointestinal diseases, as well as strong crying, agitation, fear, etc. Under these conditions, a shift in the acid-base balance towards alkalosis may occur, with the creation of conditions for the manifestations of C.
Classification(E.M. Lepsky, 1945):
1. hidden form;
2. Explicit form (laryngospasm, carpo-pedal spasm, eclampsia).
Research. Determination of the content of calcium and phosphorus in blood plasma; determination of the activity of alkaline phosphatase in blood plasma, the study of CBS, ECG.
Anamnesis, clinic. History of early misrepresentation Can be detected artificial feeding, abuse of cow's milk, flour products, lack of prevention of rickets. Attack C is provoked by feverish conditions, frequent vomiting in gastrointestinal diseases, fear, agitation, severe crying, increased ultraviolet radiation.
In a child with C, the examination should show signs of rickets.
Signs of hidden C(symptoms of increased excitability of the neuromuscular apparatus):
A) Chvostek's symptom- slight tapping at the exit of the facial nerve (between the zygomatic arch and the corner of the mouth) causes contraction or twitching muscular musculature the corresponding side of the face;
b) peroneal Lust sign - percussion behind and slightly below the head of the fibula causes dorsiflexion and abduction of the foot outward;
V) Trousseau's sign - compression of the neurovascular bundle on the shoulder causes convulsive contraction of the muscles of the hand - "obstetrician's hand";
G) Maslov's symptom - an injection in the heel causes cessation of breathing instead of its increase (carried out under the control of a pneumogram);
e) Erb's symptom - opening of the cathode applied to median nerve, causes muscle contraction at a current strength of less than 5 mA.
Signs of explicit C:
A) laryngospasm - sudden difficulty in inhaling with the appearance of a peculiar noisy breathing. With a more pronounced narrowing of the glottis - a frightened facial expression, the child “catches air” with his mouth open, cyanosis of the skin, cold sweat on the face and body. After a few seconds, a noisy breath appears and is restored normal breathing. Attacks of laryngospasm can be repeated during the day;
b) carpo-pedal spasm - tonic contraction of the muscles of the limbs, especially in the hands and feet, from several minutes to several days, which may recur. With prolonged spasm, elastic swelling appears on the back of the hands and feet.
The spastic state can also spread to other muscle groups: eye, masticatory (temporary strabismus or trismus), spasms of the respiratory muscles (inspiratory or expiratory apnea) are unfavorable prognostically, less often - a spastic state of the heart muscle (cardiac arrest and sudden death). Spasms occur smooth muscle internal organs, which leads to a disorder of urination, defecation;
V) eclampsia - clonic-tonic convulsions with involvement in the process of striated and smooth muscles of the whole body; the attack begins with twitching of facial muscles, then convulsive contractions of the limbs, respiratory muscles join, cyanosis occurs. Consciousness is usually lost at the onset of an attack. The duration of the attack is from several minutes to several hours. Tonic and clonic seizures can be isolated, combined or sequential. Clonic convulsions are more often observed in children in the first year of life, tonic - in children older than a year.
Diagnosis C is based on the identification of signs of overt or latent S. in a child with rickets.
Laboratory data: A) biochemical research blood - hypocalcemia (up to 1.2-1.5 mmol / l) against the background of a relatively elevated level of inorganic phosphorus.
b) an increase in the numbers of the numerator or a decrease in the denominator in the Gyorgy formula: P0 4 - HC0 3 -K +
Ca++ Mg++ H+
Differential Diagnosis C is carried out with diseases manifested by hypocalcemia: chronic renal failure, hypoparathyroidism, malabsorption syndrome, taking drugs that reduce calcium levels
Tab. 1.44. Differential diagnosis of spasmophilia
| sign | Spasmophilia | Hypoparathyroidism | CRF | Malabsorption syndrome |
| convulsions | Yes | Yes | +/- | Possible |
| Rachitic bone changes | Characteristically | No | Osteoporosis | Osteoporosis |
| chronic diarrhea | No | No | +/- | characteristically |
| SW. urea, creatinine | No | No | Yes | No |
| Symptoms of increased neuromuscular excitability | Yes | Yes | Yes | Yes |
| PTH↓ level, phosphorus | No | No | No | Yes |
| Blood calcium ↓ | Yes | Yes | Yes | Yes |
Treatment. Treatment goals: normalization of neuromuscular excitability, indicators of mineral metabolism; relief of convulsions and other manifestations of C, treatment of rickets.
Therapy regimen
Mandatory activities: relief of hypocalcemia, syndromic therapy of manifestations of C, treatment of rickets.
Complementary therapies: regimen, diet, vitamin therapy.
Indications for hospitalization: convulsions, eclampsia, laryngospasm.
Mode: limit as much as possible or extremely carefully perform procedures that are unpleasant for the child.
Diet: exclusion of cow's milk for 3-5 days, carbohydrate nutrition, gradual transition to a balanced, age-appropriate diet.
For eclampsia: calcium chloride or calcium gluconate 10% solution, 2-3 ml, intravenously microstream. Sodium hydroxybutyrate 50-100 mg/kg IV slowly or droperidol 0.25% solution 0.1 mg/kg IV slowly or Seduxen 0.5% solution 0.15 mg/kg IM or IV, or magnesium sulfate 25% solution, 0.8 ml/kg, intramuscularly, but not more than 8.0 ml.
With carpo-pedal spasm: inside calcium chloride or gluconate, phenobarbital, bromides.
For laryngospasm: splash on the patient cold water, press your finger on the root of the tongue, according to indications - artificial respiration, drug therapy, as in eclampsia.
After emergency care: calcium preparations inside, ammonium chloride 10% solution, 1 tsp. 3 times a day, vitamin D 4000 ME daily from 4-5 days; vitamin therapy.
Prevention C primarily associated with the detection and treatment of rickets. The rational feeding of the child is important. Special attention draw on the early introduction of cow's milk products into the diet. It is necessary to prevent strong crying, fear.
VITAMIN D HYPERVITAMINOSIS (HD) occurs with an overdose of vitamin D or with individual hypersensitivity to him.
Epidemiology. Currently, due to the revision of approaches to the prevention and treatment of rickets, HD in children is rare.
Biochemistry
Tooth tissues
Periodontium UDC 616.31:577.1
Zabrosaeva L.I. Biochemistry of tissues of the tooth and periodontium. ( Teaching aid). Smolensk, SGMA, 2007, 74 p.
Reviewers:
A.A. Chirkin, Professor, Doctor of Biological Sciences, Head of the Department of Biochemistry, Vitebsk State University. P. Masherova.
V.V. Alabovsky, professor, doctor medical sciences, Head of the Department of Biochemistry, Voronezh State Medical Academy.
The teaching aid was compiled in accordance with the curriculum of the Ministry of Education of the Russian Federation (1996) for the dental faculty of medical universities. This manual includes biochemistry questions connective tissue, tissues of the tooth and periodontium, as well as information directly related to them about phosphorus-calcium metabolism, its regulation, biochemical aspects of the mineralization of hard tissues of the tooth and bone, and the metabolic functions of fluorine.
The manual is intended for students of the Faculty of Dentistry, interns, residents. Individual chapters may be of interest to students of the medical and pediatric faculties.
Tables 2, figures 15. References 78 titles.
Smolensk, SGMA, 2007
Phosphorus-calcium metabolism and its regulation.
Calcium is one of the five (O, C, H, N, Ca) most common elements found in the human and animal body. The tissues of an adult human body contain up to 1-2 kg of calcium, 98-99% of which is localized in the bones of the skeleton. Being a part of mineralized tissues in the form of phosphate salts and apatites of various types, calcium performs plastic and supporting functions. Extraosseous calcium, which accounts for about 1-2% of its total content in the body, also performs extremely important functions:
1. Calcium ions are involved in the conduction nerve impulses, especially in the area of acetylcholine synapses, contributing to the release of mediators.
2. Calcium ions are involved in the mechanism of muscle contraction, initiating the interaction of actin and myosin when they enter the sarcoplasm. From the sarcoplasm, calcium ions are pumped out into the cisterns of the sarcoplasmic reticulum by Ca 2+ - dependent ATPase or the so-called. "calcium pump". This results in muscle relaxation.
3. Calcium ions are a cofactor for a number of enzymes involved in the synthesis of proteins, glycogen, energy metabolism and other processes.
4. Calcium ions easily form intermolecular bridges, bring molecules together, activating their interaction inside and between cells. This fact explains the participation of calcium in phagocytosis, pinocytosis, and cell adhesion.
5. Calcium ions are a necessary component of the blood coagulation system.
6. In combination with the protein calmodulin, calcium ions are one of the secondary mediators of the action of hormones on intracellular metabolism.
7. Calcium ions increase the permeability of cells to potassium ions, affect the functioning of ion channels.
8. Excessive accumulation of calcium ions inside cells leads to their destruction and subsequent death.
Calcium enters the body as part of food in the form of salts: phosphates, bicarbonates, tartrates, oxaloacetates, in total - about 1 g per day. Most calcium salts are poorly soluble in water, which explains their limited absorption in the gastrointestinal tract. In adults, an average of 30% of all dietary calcium is absorbed from the gastrointestinal tract, and more in children and pregnant women. Calcium absorption from the intestinal lumen involves Ca 2+ -binding protein, Ca 2+ -dependent ATP -ase, ATP. Vitamin D, lactose, lemon acid, proteins increase the absorption of calcium from the gastrointestinal tract, and alcohol in high doses and fats decrease it.
Calcium transport by blood occurs in combination with organic and inorganic acids, as well as with albumins and, to a lesser extent, with plasma globulins. These transport forms of calcium together make up the bound blood calcium - a kind of blood calcium depot. In addition, there is also ionized calcium in the blood, which is normally 1.1-1.3 mmol / l. The total calcium content in the blood serum is 2.2-2.8 mmol / l. Hypocalcemia occurs with rickets, hypoparathyroidism, with a low calcium content in food and a violation of its absorption in the gastrointestinal tract. Hypercalcemia is noted in hyperparathyroidism, hypervitaminosis D and other pathological conditions. The calcium ion and its paired phosphate ion are present in the blood plasma at concentrations close to the solubility limit of their salts. Therefore, the binding of calcium to plasma proteins prevents the possibility of sedimentation and ectopic tissue calcification. The change in the concentration of albumins, and to a lesser extent globulins, in the blood serum is accompanied by a change in the ratio of the concentrations of ionized and bound calcium. Acid pH shift internal environment The body promotes the transition of calcium into an ionized form, and alkaline, on the contrary, its binding to proteins.
From the blood, calcium enters the mineralized and, to a lesser extent, other tissues. In the body, bone tissue acts as a depot of calcium. The periosteum contains easily exchangeable calcium, which makes up about 1% of the total skeletal calcium. This is a mobile pool of calcium. Mitochondria, nuclei, cisterns of the sarcoplasmic and endoplasmic reticulum have the ability to accumulate calcium. They contain Ca 2+ -dependent ATPases, which carry out the release of calcium ions from the cytoplasm into the extracellular fluid associated with ATP hydrolysis (muscle contraction) and the pumping of Ca 2+ into the cisterns of the sarcoplasmic reticulum (muscle relaxation). Calcium is a typical extracellular cation. The calcium concentration inside the cells is less than 1 µmol/l. If it rises more than 1 μmol / l, then there is a change in the activity of many enzymes, which entails a disruption in the normal functioning of the cell. An increase in the permeability of cell membranes under various pathological conditions is also accompanied by an activation of the transport of calcium ions into cells. In this case, there is an increase in the activity of membrane phospholipase A 2 , the release of polyunsaturated fatty acids, activation of lipid peroxidation processes in membranes and increased formation of eicosanoids, which leads to a further increase in the permeability of membrane structures up to the development of destructive changes in them, leading to cell death. Known, for example, the so-called. "Calcium paradox" - a sharp deterioration in the function of the heart muscle and the general condition of the body in the postischemic phase of the myocardium.
Excretion of calcium from the body is carried out mainly through the intestines in the composition of bile, gastric juice, saliva and pancreatic secretions (only about 750 mg / day). Little calcium is excreted in the urine (about 100 mg / day), because. 97-99% of primary urine calcium is reabsorbed in the convoluted tubules of the kidneys. After reaching the age of 35, the total excretion of calcium from the human body increases.
Phosphorus, like calcium, is one of the vital elements. The body of an adult contains ~1 kg of phosphorus. 85% of this amount performs structural and mineralizing functions, being part of the bones of the skeleton. A significant part of phosphorus is an integral part of various organic substances: phospholipids, some coenzymes, macroergic compounds, nucleic acids, nucleotides, phosphoproteins, phosphate esters of glycerol, monosaccharides and other compounds. Participating in the reactions of phosphorylation and dephosphorylation of various organic compounds, phosphate performs a regulatory function. These processes occur with the participation of specific protein kinases. In this way, the activity of many key enzymes is regulated: phosphorylase, glycogen synthase, as well as nuclear, membrane proteins and other compounds. Inorganic phosphate is part of the phosphate buffer system: NaH 2 PO 4 / Na 2 HPO 4 and thereby participates in maintaining the acid-base state of blood and tissues.
The main source of phosphorus for the human body is food. The content of phosphorus in the daily human diet varies from 0.6 to 2.8 g and depends on the composition and amount of food consumed. The main amount of phosphorus comes in the composition of milk, meat, fish, flour products and, to a lesser extent, with vegetables. In the gastrointestinal tract, phosphorus is absorbed better than calcium: 60-70% is absorbed food phosphorus. The exchange of phosphorus is closely related to the exchange of calcium, starting with intake into the body as part of food and ending with excretion from the body. They are also united by the general endocrine regulation.
In blood plasma, phosphorus is in three forms: ionized (55%), associated with proteins (10%), associated with complexons Na, Ca, Mg (35%). Normally, the content of inorganic phosphate in the blood serum of an adult is 0.75 - 1.65 mmol / l and depends on age, sex, diet, etc. In the blood serum of children, the content of inorganic phosphate is higher than in adults and depends on the intensity of growth. Hyperphosphatemia is noted in chronic renal failure, bone fracture healing, pituitary gigantism, some bone tumors, hypervitaminosis D. Hypophosphatemia occurs with rickets, hyperparathyroidism, low phosphorus content in food and impaired absorption in the intestine, as well as when a large amount of phosphorus is ingested carbohydrates. The content of phosphates in blood cells exceeds their content in plasma by 30-40 times. In cells, unlike blood plasma, organic phosphate predominates, for example, in erythrocytes - 2,3 diphosphoglycerate, ATP, glucose-6 phosphate, phosphotrioses and other phosphoric acid esters of organic substances. The concentration of organic phosphate in the cell is almost 100 times higher than the inorganic one. The blood plasma is dominated by inorganic phosphate, which, entering the cells, is used for phosphorylation reactions of various organic substances. It has been shown, for example, that the entry of an increased amount of glucose into the cells is accompanied by a decrease in the content of inorganic phosphate in the blood plasma.
The role of the phosphorus depot is performed by the bones of the skeleton, which include phosphorus in the form of various types of apatites and phosphorus-calcium salts. Excretion of phosphorus from the body is carried out mainly through the kidneys (64.4%), as well as with feces (35.6%). A negligible amount of phosphorus is excreted in sweat. In the convoluted tubules of the kidneys, up to 90% of phosphorus is reabsorbed. Phosphorus reabsorption is dependent on sodium reabsorption. Increased urinary sodium excretion is accompanied by increased phosphorus excretion. Monosubstituted phosphates (NaH 2 PO 4) predominate in the composition of urine, and disubstituted phosphates (Na 2 HPO 4) prevail in blood plasma. In urine, the ratio of NaH 2 PO 4 / Na 2 HPO 4 is 50/1, and in blood plasma it is 1/4.
Parathyroid hormone, calcitonin, vitamin D are involved in the regulation of phosphorus-calcium metabolism. Parathyroid hormone (PTH) is synthesized in the parathyroid glands ( steam organ), as well as partially in the thymus and thyroid gland. By chemical structure is a protein with a molecular weight of 9500, consisting of 84 amino acids. It is produced as a preprohormone (115 amino acids), by partial proteolysis it is converted into a prohormone (90 amino acids), and then into active PTH (84 amino acids). The synthesis and secretion of PTH increase with a decrease in the concentration of calcium in the blood. The half-life of PTH is 20 minutes, its target organs are bone and kidneys. In the bones, PTH (in large doses) stimulates the breakdown of collagen and the transfer of calcium and phosphorus from bone to blood, in the kidneys it increases calcium reabsorption, but reduces phosphorus reabsorption, which leads to phosphaturia and a decrease in the concentration of phosphorus in the blood. This increases the calcium concentration in the blood. PTH also promotes the conversion of vitamin D in the kidneys to its active form, calcitriol (1,25 dihydroxycholecalciferol). In this regard, it can indirectly (through calcitriol) activate calcium absorption in small intestine.
The secretion of PTH depends only on the concentration of calcium in the blood and is not controlled by other glands. internal secretion. The concentration of phosphorus in the blood plasma does not affect the secretion of PTH. Insufficiency of the function of the parathyroid glands can develop during operations on the neck, accidental removal or damage to the parathyroid glands, as well as due to their autoimmune destruction. The apparent effect of hypoparathyroidism may be associated with a decrease in the sensitivity of target organ receptors to parathyroid hormone. Clinical symptoms of hypoparathyroidism are hypocalcemia, hyperphosphatemia, increased neuromuscular excitability, convulsions, tetany. Death may occur due to spasm of the respiratory muscles and laryngospasm. The effects of hypocalcemia can be eliminated by introducing calcium, parathyroid hormone, and vitamin D preparations into the body.
Hyperparathyroidism is manifested by hypercalcemia, hypophosphatemia, phosphaturia, bone resorption, leading to frequent fractures bones; kidney stone formation, nephrocalcinosis, decreased kidney function. Causes of hyperparathyroidism can be parathyroid adenoma, as well as some pathological conditions kidneys, leading to a decrease in the formation of calcitriol in the kidneys and a decrease in the concentration of calcium in the blood. In response to hypocalcemia, the production and secretion of PTH increases. Persistent hypercalcemia can lead to coma and death from muscle paralysis.
Calcitonin is a 32 amino acid peptide with Mr 3200. It is synthesized in the thyroid and parathyroid glands, secreted in response to hypercalcemia, reducing the concentration of calcium and phosphorus in the blood. The mechanism of action of calcitonin is that it inhibits the mobilization of calcium and phosphorus from the bone, promotes bone mineralization. Calcitonin is a PTH antagonist, as it maintains the "tone" of calcium in the blood. With hyperproduction of calcitonin, osteosclerosis can develop - an increase in bone mass per unit of its volume.
Vitamin D is a group of substances - calciferols with anti-rachitic activity. The most important among them - cholecalciferol (vitamin D 3), ergocalciferol (vitamin D 2) and dihydroergocalciferol (vitamin D 4) belong to the group of steroid compounds. Vitamin D 3 is found in food of animal origin: in fish oil, liver, egg yolk, butter. This vitamin can also be synthesized in the skin from cholesterol under the influence of ultraviolet rays (endogenous vitamin D 3). Ergocalciferols are of plant origin. However, neither ergo- nor cholecalciferols have biological activity. Their biologically active forms are formed during metabolism. Dietary and endogenous calciferols are brought into the liver with blood flow. In hepatocytes, with the participation of a specific monooxygenase system, including calciferol 25-hydroxylase, NADH, and molecular oxygen, the first stage of vitamin D 3 hydroxylation occurs, resulting in the appearance of an OH group at the 25th carbon atom.
Then 25 (OH) derivative of vitamin D 3 is transferred to the kidneys with the help of calciferol-binding protein of blood plasma, where it undergoes the second stage of hydroxylation with the participation of 1 alpha-hydroxylase of calciferols, NADH, molecular oxygen and turns into 1,25 dihydroxycholecalciferol, or calcitriol, a biologically active form of vitamin D (Fig. 1).
Fig.1. Formulas of the precursor of vitamin D 3 - -7 dehydrocholesterol, vitamin D 3 and calcitriol.
Calcitriol (1,25 dihydroxycholecalciferol) has the following bodies- targets: intestines, bone tissue, kidneys. In the intestine, it increases the absorption of calcium and phosphorus against a concentration gradient involving ATP and calcium-binding protein, the formation of which occurs under the action of calcitriol. In mineralized tissues, calcitriol in physiological doses increases the synthesis of collagen, calcium-binding proteins, sialoglycoproteins of the intercellular substance, as well as the specific dentin protein phosphophorin and specific enamel proteins: amelogenins, enamelins, contributing to their mineralization. In the renal tubules, it activates the reabsorption of calcium and phosphorus. As a result, vitamin D determines the optimal content of calcium and phosphorus in the blood plasma, which is necessary for the mineralization of bone tissue, tooth and periodontal tissues. The biological function of vitamin D can also be described as calcium, phosphorus-sparing.
With vitamin D deficiency, rickets develops in the body of children. Main clinical symptoms rickets: a decrease in the concentration of calcium and phosphorus in the blood, a violation of the mineralization of bone tissue, which leads to deformation of the supporting bones of the skeleton. Muscle atony, late teething, and violation of the dentition are also characteristic. Most often, the causes of rickets are insufficient content of vitamin D in food, impaired absorption of it in the gastrointestinal tract, as well as insufficient action of ultraviolet rays on the body. In children with pathology of the liver and kidneys, there are also forms of rickets associated with a violation of the conversion of calciferols into their active forms. The cause of rickets can also be a genetically determined deficiency of monooxygenase systems that are involved in the formation of biologically active forms of vitamin D 3 . In some cases, the development of rickets may be due to the absence or insufficiency of calcitriol receptors.
Vitamin D deficiency in adults causes osteomalacia (softening of the bones), calcium malabsorption in the small intestine, and hypocalcemia, which can lead to overproduction of PTH. In the treatment of rickets, vitamin D, calcium and phosphorus preparations, adequate sun exposure and ultraviolet radiation, as well as the elimination of liver and kidney pathology are used. Hypervitaminosis D leads to bone demineralization, fractures, elevated blood levels of calcium and phosphorus, soft tissue calcification, and kidney stones and urinary tract. The daily requirement for vitamin D for adults is 400 IU, for pregnant and lactating women - up to 1000 IU, for children - 500-1000 IU, depending on age.
PhysiologyMineral metabolism disorders are changes in the level of calcium, phosphorus or magnesium. Calcium is essential for cell function. In the process of regulating the homeostasis of these main mineral macronutrients, three organs are mainly involved - the kidneys, bones and intestines, and two hormones - calcitriol and parathyroid hormone.
The role of calcium in the body
About 1 kg of calcium is contained in the skeleton. Only 1% of the total body calcium circulates between the intracellular and extracellular fluids. Ionized calcium makes up about 50% of the total calcium circulating in the blood, about 40% of which is bound to proteins (albumin, globulin).
When assessing the level of calcium in the blood, it is necessary to measure the ionized fraction or both total calcium and blood albumin, on the basis of which the level of ionized calcium can be calculated using the formula (Ca, mmol / l + 0.02x (40 - albumin, g / l).
The normal level of total calcium in the blood serum is 2.1-2.6 mmol/L (8.5-10.5 mg/dL).
The role of calcium in the body is diverse. We list the main processes in which calcium takes part:
provides bone density, being the most important mineral component in the form of hydroxyapatite and carbonate apatite;
participates in neuromuscular transmission;
regulates cell signaling systems through work calcium channels,
regulates the activity of calmodulin, which affects the functioning of enzyme systems, ion pumps and cytoskeletal components;
participates in the regulation of the coagulation system.
homeostasis of calcium and phosphorus
The following are the main mechanisms involved in the regulation of calcium levels.
The active metabolite of vitamin D - the hormone calcitriol (1,25 (OH) 2calciferol) is formed in the process of hydroxylation of cholecalciferol under the action of sun rays and with the participation of two main hydroxylation enzymes - 25-hydroxylase in the liver and 1-a-hydroxylase in the kidneys. Calcitriol is the main hormone that stimulates the absorption of calcium and phosphorus in the intestine. In addition, it enhances the reabsorption of calcium and excretion of phosphorus in the kidneys, as well as the resorption of calcium and phosphorus from the bones, like parathyroid hormone. The level of calcitriol is regulated directly by blood calcium, as well as by the level of parathyroid hormone, which affects the activity of 1-a-hydroxylase.
The calcium-sensitive receptor is located on the surface of the cells of the parathyroid glands and in the kidneys. Its activity normally depends on the level of ionized calcium in the blood. An increase in the level of calcium in the blood leads to a decrease in its activity and, as a result, a decrease in the level of secretion of parathyroid hormone in the parathyroid gland and an increase in calcium excretion in the urine. On the contrary, with a decrease in the level of calcium in the blood, the receptor is activated, the level of secretion of parathyroid hormone increases and the excretion of calcium in the urine decreases. Defects in the calcium-sensitive receptor lead to impaired calcium homeostasis (hypercalciuric hypocalcemia, familial hypocalciuric hypercalcemia).
Parathyroid hormone is synthesized by the cells of the parathyroid glands. It exerts its effect through a G-protein-coupled receptor on the surface of cells of target organs - bones, kidneys, intestines. In the kidneys, parathyroid hormone stimulates the hydroxylation of 25 (OH) D with the formation of the hormone calcitriol, which plays one of the main roles in the regulation of calcium homeostasis. In addition, parathyroid hormone increases calcium reabsorption in the distal nephron, increases calcium absorption in the intestine. The effect of parathyroid hormone on bone metabolism is twofold: it enhances both bone resorption and bone formation. Depending on the level of parathyroid hormone and the duration of exposure to its high concentration, the state of the bone tissue in different sections (cortical and trabecular) changes differently. In calcium homeostasis, the dominant effect of parathyroid hormone is to increase bone resorption.
Parathormone-like peptide is structurally identical to parathyroid hormone only in the first eight amino acids. However, it can bind to the parathyroid hormone receptor and have the same effects. The clinical significance of parathyroid hormone is only in malignant tumors that can synthesize it. In normal practice, the level of parathormone-like peptide is not determined.
Calcitonin is synthesized in the C-cells of the thyroid gland, stimulates the excretion of calcium in the urine, and inhibits the function of osteoclasts. A significant role of calcitonin in calcium homeostasis in fish and rats is known. In humans, calcitonin does not have a pronounced effect on blood calcium levels. This is confirmed by the absence of disturbances in calcium homeostasis after thyroidectomy, when C-cells are removed. The level of calcitonin is of clinical significance only for the diagnosis of malignant tumors - C-cell cancer thyroid and neuroendocrine tumors, which can also synthesize calcitonin (insulinoma, gastrinoma, VIPoma, etc.).
Glucocorticoids normally do not significantly affect the level of calcium in the blood. IN pharmacological doses Glucocorticoids significantly reduce calcium absorption in the intestine and reabsorption in the kidneys, thereby lowering the level of calcium in the blood. High doses of glucocorticoids also affect bone metabolism by increasing bone resorption and reducing bone formation. These effects are of importance in patients receiving glucocorticoid therapy.
In blood calcium (Ca) is in three different forms. Approximately half of the calcium is in the form of non-filterable, poorly soluble compounds with proteins. The other half is free ultrafilterable calcium, able to pass through cell membranes, while 1/3 of its part is in the ionized form. Exactly ionized calcium plays a major role in the regulation of all physiological processes.
Functions of calcium in the body:
- Regulation of all processes occurring in the body.
- Calcium is the main universal regulator of cell activity.
- Calcium is an antioxidant.
- Musculoskeletal function. In children of the first year of life, the rate of destruction and construction of bone tissue is 100%, in older children - 10%, in adults - 2-3%. As a result, during periods of intensive growth in children and adolescents, the skeleton is completely renewed in 1-2 years. Peak bone mass is usually reached by age 25. By the age of 40-50, destruction processes can exceed construction. The result is bone loss, or osteoporosis. It has been established that insufficient calcium intake in childhood and adolescence leads to a decrease in peak bone mass by 5-10%, which increases the incidence of hip fracture at age by 50%.
- Maintenance of calcium homeostasis in the body.
- Alkalinization of body fluids. One of the main functions of calcium. For example, the results of analyzes in incurable cancer patients (pak III and IV degrees) showed that not all of them had a pronounced calcium deficiency. Such patients were prescribed calcium and vitamins, and in some cases there was a significant positive effect. Thus, the alkaline environment prevents the development of cancer.
- Regulation of neuromuscular excitability.
- Normalization of the activity of the heart and blood vessels: normalization contractile activity heart, rhythm and conduction, blood pressure, anti-atherosclerotic action.
- It is an essential component of the blood coagulation system.
- Has anti-inflammatory, anti-allergic effect.
- Provides body resistance to external unfavorable factors.
How much calcium does the human body need?
On average, an adult should consume about 1 g of calcium per day, although only 0.5 g is required for the constant renewal of tissue structure. This is due to the fact that calcium ions are absorbed (absorbed in the intestines) by only 50%, because poorly soluble compounds are formed. A growing body, pregnant and lactating women, people with increased physical and emotional stress, as well as people who are bedridden, require increased amount calcium - approximately 1.4 - 2 g per day. IN winter period more calcium is needed.
It must be remembered that calcium is well absorbed by the body only from foods that are not subjected to heat treatment. During heat treatment, organic Ca instantly passes into an inorganic state and is practically not absorbed by the body.
Factors affecting the absorption of calcium by the body
1. Must be taken with protein food, with amino acids (as calcium transporters into the cell are amino acids).
2. Calcium preparations should be washed down with 1 glass of liquid with lemon juice, which increases the absorption of calcium salts. This is especially important for people with low gastric acidity, which decreases with age and various diseases.
3. It is necessary to ensure sufficient drinking regimen: at least 1.5 liters of fluid per day (maximum up to 14 hours, taking into account the biorhythm of the kidneys). With constipation, the amount of fluid should increase.
4. Bile acids also promote the absorption of calcium. In various diseases of the gallbladder associated with a decrease in its function, calcium intake should be combined with the intake of choleretic agents.
5. Vitamin D and parathyroid hormones contribute to the absorption of calcium in the intestines and the deposition of calcium and phosphorus in the bones.
6. For the absorption of calcium, vitamins such as A, C, E and trace elements - magnesium, copper, zinc, selenium are required, and in a strictly balanced form.
Diseases requiring the appointment of calcium, due to its deficiency:
- diseases of the central nervous system;
- oncological diseases;
- rickets;
- malnutrition;
- diseases of the joints (arthritis, osteoporosis, etc.);
- diseases of the gastrointestinal tract (acute pancreatitis (calcium deficiency disrupts the production of pancreatic enzymes), gastritis, peptic ulcer, malabsorption syndrome or impaired intestinal absorption, biliary dyskinesia, cholelithiasis, etc.);
- cardiovascular diseases(atherosclerosis, ischemic heart disease, myocardial infarction, stroke, arterial hypertension, rhythm and conduction disturbances);
- rheumatic diseases (it has been established that calcium deficiency in children is noted already at the very beginning of the disease);
- chronic diseases kidney, renal failure;
- dermatological diseases (psoriasis, atopic dermatitis, allergic reactions) - the basis of the therapeutic effect is alkalization of the body;
- endocrine pathology(hypoparathyroidism, diabetes 1 type, etc.);
- cystic fibrosis;
- chronic lung diseases (it has been established that with increased bronchial secretion, there is a loss of calcium);
- anemia (always accompanied by calcium deficiency, which leads to iron deficiency, therefore, in oncology, with STD, with gastrointestinal diseases - anemia - due to calcium deficiency);
- dysplasia ("weakness") of the connective tissue (myopia, mitral valve prolapse, orthopedic pathology - flat feet, scoliosis, chest deformity, even small).
Conditions that require the appointment of calcium, due to its increased costs by the body:
- sports, increased physical activity;
- pregnancy, breastfeeding;
- menopause;
- periods of rapid growth in children and adolescents;
- stress;
- immobilization;
- winter period;
- preoperative and postoperative.
What diseases cause a violation of calcium metabolism
Causes of calcium metabolism disorders:Causes of excess calcium
Vitamin D overdose, some diseases with impaired mineral metabolism (rickets, osteomalacia), bone sarcoidosis, Itsenko-Cushing's disease, acromegaly, hypothyroidism, malignant tumors.
Consequences of excess calcium
An overdose of calcium greater than 2 g can cause hyperparathyroidism.
Initial signs: growth retardation, anorexia, constipation, thirst, polyuria, muscle weakness, depression, irritation, hyperreflexia, dizziness, imbalance when walking, inhibition of the knee jerk (and others), psychosis, memory lapses.
With prolonged hypercalcemia, calcification develops, arterial hypertension, nephropathy.
Causes of calcium deficiency
- Hypoparathyroidism, spasmophilia, diseases of the gastrointestinal tract, endocrine diseases, renal failure, diabetes mellitus, vitamin D hypovitaminosis.
Contribute to calcium deficiency in the body:
- Sedentary and sedentary lifestyle. Immobilization causes a decrease in the absorption of calcium in the gastrointestinal tract.
- One of the causes of calcium deficiency in the body is its low (less than 8 mg / l) content in natural water. Water chlorination causes additional calcium deficiency.
- Stress.
- Many drugs (hormonal, laxatives, antacids, diuretics, adsorbents, anticonvulsants, tetracycline). Calcium can form compounds with tetracyclines that are not absorbed in the intestine. At long-term use tetracycline, they are washed out of the body, and there is a need for replenishment from the outside.
- High protein intake. An increase in the daily amount of animal proteins by 50% causes the excretion of calcium from the body by 50%.
- Consumption of a large amount of sugar (when dissolved in the stomach, it interferes with the absorption of calcium, disrupts phosphorus-calcium metabolism).
- Consumption of a large amount of salt (it helps to remove calcium from the body)
- It has been established that when cooking and frying products, organic calcium in them turns into inorganic, which is practically not absorbed.
- Other products with an acidic reaction (animal fats, premium flour products, oxalic acid, spinach, rhubarb) lead to a violation of calcium metabolism.
- Early artificial feeding of children under one year old, since calcium in artificial mixtures is absorbed by 30%, and from breast milk by 70%. This covers the daily need of an infant for calcium, provided that the nursing mother is properly fed.
Consequences of calcium deficiency
Initial signs: tension, irritability, bad hair, nails, teeth. Calcium deficiency in children can manifest itself in the desire to eat dirt and paint.
- A lack of calcium also affects the muscles, contributing to their spasm and a feeling of leakage, up to seizures(tetany). Hand tremors (convulsive readiness), nocturnal muscle cramps; hypokalemic morning cramps. - This includes spasms of the intestines, which are called spastic colitis or spastic constipation. Premenstrual syndrome and spasmodic abdominal pain in women during menstruation due to calcium deficiency.
- In the future, osteoporosis develops. Calcium is always present in the blood, and if it is not supplied with food supplements and food, it is washed out of the bones. This is manifested by pain in the bones, in the muscles. The risk of fractures increases with the smallest loads, the most dangerous and most frequent of which is a fracture of the femoral neck.
- Calcium deficiency contributes to the development of atherosclerosis, arthrosis, osteochondrosis, hypertension.
- Deficiency of calcium and magnesium worsens the course of allergic diseases.
Which doctors to contact if there is a violation of calcium metabolism
EndocrinologistPediatrician
Therapist
Family doctor
