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Thyroxine (T4) is one of the two main hormones thyroid gland, the main function of which is the regulation of energy and plastic metabolism in the body. Free thyroxine is the biologically active part of total thyroxine, which plays important role in metabolism.

Synonyms Russian

Free T4, free tetraiodothyronine.

SynonymsEnglish

Thyroxine, Free T4.

Research method

Chemiluminescent immunoassay.

Units

Pmol/L (picomoles per liter).

What biomaterial can be used for research?

Venous blood.

How to properly prepare for research?

Do not eat for 2-3 hours before the test (you can drink clean still water).
Stop taking steroid and thyroid hormones 48 hours before the test (in consultation with your doctor).
Avoid physical and emotional stress 24 hours before the test.
Do not smoke for 3 hours before the test.

General information about the study

The analysis determines the concentration in the blood of the non-protein-bound fraction of the main thyroid hormone, thyroxine (T4). This is one of the most important tests for assessing the function of the thyroid gland; its results do not depend on the concentration of proteins that bind thyroxine in the blood plasma, and reveal the level of only the active part of the hormone. More often this test prescribed in conjunction with concentration measurement thyroid-stimulating hormone(TSH) – regulator of thyroid function. The thyroid gland controls metabolism and the rate of energy consumption by the body. She works according to the mechanism feedback with the pituitary gland. The pituitary gland releases thyrotropin (TSH) in response to a decrease in the concentration of thyroxine (T4), thereby stimulating the thyroid gland to produce hormones. When thyroxine levels increase, the pituitary gland begins to produce less thyroid-stimulating hormone and the secretion of thyroxine by the thyroid gland decreases.

Thyroxine (T4) makes up about 90% of the total amount of hormones secreted by the thyroid gland. In the blood, T4 is found either free or bound to globulin proteins. The bulk of all thyroxine is in bound form and only 0.1% is in free form. It is the free fraction of the T4 hormone that is the most biologically active.

If the thyroid gland is unable to produce required amount thyroxine or not enough thyroid-stimulating hormone is produced to stimulate it, symptoms of hypothyroidism appear. In patients with reduced level T4 increases body weight, skin dries, fatigue increases, they become very sensitive to cold, in women it is impaired menstrual cycle. If the level of free T4 is higher than normal, metabolic processes in the body and the production of energy in the cells increases, which leads to hyperthyroidism, which is characterized by rapid heartbeat, anxiety, weight loss, sleep disturbance, trembling hands, dry and red eyes, and swelling of the face.

The most common cause of thyroid hormone imbalance is autoimmune damage to the gland. This may be Graves' disease (causes hyperthyroidism with increased free T4) or Hashimoto's thyroiditis (causes hypothyroidism - low free T4).

What is the research used for?

To diagnose thyroid dysfunction and monitor their treatment.
To diagnose the causes of female infertility.
For the diagnosis of congenital hypothyroidism.

When is the study scheduled?

For symptoms of hyperthyroidism: rapid heartbeat, increased irritability, weight loss, insomnia, hand tremors, weakness, fatigue, diarrhea (in some cases), hypersensitivity to light, blurred vision, swelling around the eyes, dryness, redness, protrusion of the eyeballs.
For symptoms of hypothyroidism: weight gain, dry skin, constipation, cold intolerance, swelling, hair loss, irregular menstruation among women. With advanced hypothyroidism, complications such as cardiac arrhythmias, ischemia of the heart muscle, and coma can develop. In children, hypothyroidism sometimes causes delays in physical and mental development– cretinism.
During a preventive (for example, annual) examination together with other laboratory tests(general blood and urine analysis, various biochemical indicators).
To monitor the treatment of thyroid diseases - periodically together with the study of thyroid-stimulating hormone (at least once every 3 months).
Pregnant women who are predisposed to or suffering from thyroid diseases - for timely detection disturbances in the secretion of thyroid hormones (they can lead to termination of pregnancy or congenital pathology fetus).
In the first days of life for newborns born to mothers with thyroid diseases.

What do the results mean?

Reference values (free T4 norm)

During pregnancy

Reasons for increasing free T4 levels

Diffuse toxic goiter.
Thyroiditis.
Thyroid adenoma.
TSH-independent thyrotoxicosis.
Obesity.
Postpartum thyroid dysfunction.
Kidney diseases.
Chronic liver pathology (hepatitis, cirrhosis, etc.).
Heparin therapy.

Reasons for decreased free T4 levels

Primary hypothyroidism.
Endemic goiter.
Autoimmune thyroiditis.
Resection of the thyroid gland.
Secondary hypothyroidism.
Thyrotropinoma.
Inflammatory processes in the pituitary gland and hypothalamus.
Lack of iodine.
Protein deficiency (depletion).
Lead poisoning.
Heroin addiction.
Taking oral contraceptives.

What can influence the result?

Thyroxine levels may be elevated when taking the following medications: amiodarone, levothyroxine, propranolol, propylthiouracil, aspirin, danazol, furosemide, tamoxifen, valproic acid.
Reception anabolic steroids, phenytoin, carbamazepine, thyreostatics, clofibrate, lithium preparations, methadone, octreotide can reduce the level of tyrcosine.

Who orders the study?

Endocrinologist, therapist, pediatrician, gynecologist, neurologist, surgeon.

To ensure energy metabolism in all human cells and organs, various hormones are needed, and most of them are produced by the thyroid gland, which is controlled by a part of the brain - the pituitary gland.

Upper section The pituitary gland is responsible for the hormone that affects the production of the thyroid gland:

T3 – triiodothyronine;
T4 – thyroxine.

T4 is more active; under the influence of the enzyme thyroid peroxidase (TPO), it is converted into T3. In the blood, they are combined into protein compounds and circulate in this form, and if necessary, they leave the ligament and are released. Such free hormones T3 and T4 provide basic metabolic and biological activity. The level of free hormones in the blood is less than 1% of the total, but these indicators are important for diagnosis.

How T4 and T3 act in the body

Acting interconnectedly, iodinated polypeptide hormones affect general development body, activating all systems. As a result of coordinated work:

blood pressure stabilizes;
heat is generated;
motor activity increases;
the saturation of all organs with oxygen accelerates;
mental processes are stimulated;
normal frequency and rhythm of heart contractions are developed;
the absorption of proteins is accelerated;
Hormones participate in all metabolic processes, enriching the cells and tissues of the body with energy.

Deviation from the norm of any of the hormones, more or less, leads to an imbalance and can cause various abnormalities:

decreased intellectual abilities;
disturbance of mental activity;
lowering blood pressure;
disruptions in contractions of the heart muscle;
the occurrence of body edema;
disturbances in the functioning of the reproductive system, including infertility;
the functionality of the gastrointestinal tract is impaired;
development coronary disease hearts.

If the level of T3, T4 and TSH decreases sharply during pregnancy, this can cause a disruption in the formation of nervous system in the fetus.

The value of tests

To diagnose the condition of the thyroid gland, the doctor will prescribe an analysis for all three hormones - T3, T4 and TSH, and quantitative indicators in the free state will be determined and general level:

TSH - regulates the production of hormones; if its level begins to increase, the thyroid gland produces T4 and T3 to a lesser extent - this deviation is called hypothyroidism;
free hormone T4 is responsible for the production of proteins in the body, its deviations from the norm indicate a malfunction of the thyroid gland;
the overall level of thyroxine is affected by the concentration of transport proteins in the blood;
Free T3 is involved in oxygen metabolism and its absorption by cells.

The free T3 hormone is formed as a result of the synthesis of T4, which differs only in one iodine atom in the molecule.

Norms of T3, T4 and TSH for different groups of people

Patients	TSH, µIU/ml	T3 SV	T3 general	T4 SV	T4 general
Adults	0,4–3,9	2,6–5,5	0,9–2,7	9,0–19,0	62,0–150,7
Pregnant	0,1–3,4	2,3–5,2	1,7–3,0	7,6–18,6	75,0–230,0
Children:
1–5 years	0,4–6,0	–	1,30–6,0	–	90,0–193,0
6–10 years	0,4–5,0	–	1,39–4,60	10,7–22,3	82,0–172,0
11–15 years	0,3–4,0	–	1,25–4,0	12,1–26,8	62,0–150,7

The norm for women is the same as for men.

Why there may be an imbalance of T4 and T3

The consequences of a lack or excess of T4 T3 hormones affect all systems of the body, and the causes of imbalance are abnormalities in the functioning of the thyroid gland or pituitary gland:

toxic goiter (or forms);
toxic adenoma;
pituitary tumor;
oncological diseases of the thyroid gland.

During pregnancy occurs hormonal imbalance and the production of T4 and T3 may be impaired, most often the level of 3T is reduced, especially in the first and second trimester. For normal development fetus, it needs iodine, and since its own thyroid gland is not yet formed, it draws supplies from the mother’s body. To compensate for the deficiency, the thyroid gland begins to produce T3 to a greater extent, while the secretion of TSH by the pituitary gland sharply decreases. If the deviation from the norm in a pregnant woman is close to zero, then this indicator should be alarming and requires a more detailed study.

The problem of diagnosing hormone levels in pregnant women is due to the fact that the symptoms are very similar to toxicosis and many women, and even doctors, do not pay due attention to them.

What do deviations from the norm of the T3 hormone indicate?

The main thing that the T3 hormone is responsible for is metabolic processes in the body, so its deficiency will contribute to:

frequent illnesses;
reduction protective functions body;
inability of tissues to recover after injury.

You can determine that T3 levels are low by the following signs:

pale skin;
decreased body temperature;
memory impairment;
constipation;
poor digestion of food.

A decrease in T3 levels is observed in the following diseases:

anorexia nervosa;
liver pathologies;
thyroiditis;
eclampsia (in pregnant women).

When triiodothyronine levels are low in children, it can lead to mental retardation

If free T3 is elevated, this may be evidence of the following diseases:

toxic goiter;
choriocarcinoma;
myeloma;
peripheral vascular resistance;
thyroiditis.

You can determine whether the norm has been exceeded in men by several signs:

decreased potency;
lack of sexual desire;
shaping the figure according to female type(enlargement of the mammary glands, the appearance of a fatty layer in the lower abdomen).

If the hormone is in excess in women, it can provoke:

painful and irregular menstruation;
frequent increases in temperature;
sudden weight gain or, conversely, weight loss;
mood swings, emotional outbursts;
trembling fingers.

A child may have elevated hormones if:

heavy metal poisoning;
neuropsychic disorders;
due to excessive physical activity on the body;
development

What is the effect of low and high T4 levels?

T4 hormone, responsible for protein synthesis and delivering it to cells, also has big influence on female body– reproductive function depends on it.

If the T4 hormone level is reduced, women may experience the following symptoms:

high fatigue;
tearfulness;
muscle weakness;
hair loss;
weight gain;
heavy menstruation;
ovulation failures.

If free T4 is elevated in men, they may feel:

weakness and increased fatigue;
irritability;
increased heart rate;
sweating;
weight loss;
tremor of fingers.

When the T4 norm is exceeded, this may indicate the following diseases:

porphyria;
toxic adenoma;
thyrotropinoma;
tumor diseases of the pituitary gland;
hypothyroidism;

Most often, T4 is elevated in a child with toxic goiter, when it occurs and greatly increases in volume. In second place among the reasons is taking medications, such as:

levothyroxine;
propranolol;
aspirin;
tamoxifen;
furosemide;
valproic acid.

The total T4 hormone can increase only when the child has been taking these drugs for a long time. If such medications are prescribed to a child, they should be given strictly as prescribed by the doctor.

T3, T4 free and general - what's the difference?

Both hormones circulate in the blood in two states:

free;
bound transport proteins.

The general indicator is the totality of free and bound hormones.

The effects of total and free T4 on the body are very different. The overall indicator may be outside the normal range, but the amount of free hormone will be greatly reduced. Therefore, information about free T4 and T3 is important for adequate analysis. When bound to protein, thyroxine and triiodothyronine have no effect on the body. They can circulate through the bloodstream for months and accumulate. But if the breakdown process is disrupted, then there will be a shortage of free hormones. That is why an analysis is necessary to determine free T4 and T3, as well as their total level.

It is difficult to determine which indicator is more important: total or free T4. The most revealing analysis is during pregnancy. At this time, the amount of protein in the blood increases greatly in the woman’s body, which concentrates thyroxine, so it general indicator may be normal, but there will be a lack of free T4 hormone, which will negatively affect the development of the fetus.

How to determine hormone levels

To evaluate the functioning of the thyroid gland or if there are one or more symptoms of hormone imbalance, the endocrinologist will prescribe. Before taking a test for the hormone T4, T3, TSH, you need to prepare:

stop taking it in a month;
two days before eliminating medications that contain iodine;
eliminate physical activity for two days;
try not to be nervous;
Stop eating 12 hours before and drink only water
You need to take a hormone test on an empty stomach, in the morning;

A dynamic analysis of free T4 will be more revealing; it must be taken once a month for six months.

When a doctor gives a patient referrals for tests, suspecting problems with the thyroid gland, they often include TSH, T3 and T4 values. You should know what this is important indicators, determining the presence of certain diseases. The meanings and why such analyzes are actually needed are not always clear, but they are necessary for monitoring and staging correct diagnosis to TTG norm and T4 in the blood corresponded to age.

The hormone we are interested in, called T4, belongs to the group of iodothyronines. It consists of the amino acids tyrosine and iodine atoms. It can also be seen under other names: thyroxine and tetraiodothyronine. The hormone received its designation according to the number of iodine atoms (T4). Due to its simple structure, it can be easily obtained in laboratory conditions artificially and without much difficulty to determine the amount in the blood. It is protein in nature, like the hormone insulin or adrenaline.

The thyroid gland is an important organ and is responsible for the production of various hormones, including T4. Thyrocytes, otherwise known as thyroid cells, take up essential amino acids, producing thyroglobulin. It is considered a precursor of thyroxine. It is stored in special storage facilities or follicles. When the need arises, thyroglobulin is released when cut into fragments and enters the blood, already synthesized into the T4 hormone.

The main purpose of the hormone under study is considered to be the release of energy reserves from accumulated substrates in the body, which include fats and glycogens. To understand in practice how it works, it is enough to take a certain amount of medicine, of course, only on the recommendation of a doctor, and not as an experiment, and feel the effect. The main manifestations will be increased heart rate, nervousness, and irritation. Processes occur in the body that lead to weight loss. Many corporations annually conduct testing on willing, mostly women, in search of the ideal weight loss product. However, similar symptoms appear only in case of overdose. In normal doses, the hormone does not cause any harm to well-being, leaving the heartbeat and excitability normal.

T4 cannot be called the most active in thyroid gland hormone. Triiodothyronine or T3 is much more active, about 10 times. Thyroid cells produce it in not too large quantities. The main part is created from thyroxine in the human body. While being synthesized, it is not used to its full extent.

Thyroxine and triiodothyronine have another name - thyroid hormones, that is, formed in the thyroid gland, in contrast to TSH. The latter is created in the pituitary gland. During examination, patients quite often receive referrals for tests that contain TSH and T4, T3, but this is not the same thing. Eat significant differences between them.

Function of the hormone T4 in the body

T4 or thyroxine in the blood is bound to a protein called thyroxine-binding globulin. TSG captures and delivers hormone molecules to the necessary areas of the human body. When T4 is produced, the protein immediately grabs it to begin transport. In a state not associated with TSH, thyroxine is called free and has the main biological effect in the body. When combining T4 levels with TSH and free thyroxine, we mean general analysis to the hormone thyroxine.

Free hormones bear the main burden, therefore, if a pathology is suspected, it is recommended to determine their quantity in the blood serum, which reflects the real picture and helps in making the correct diagnosis and prescribing treatment. T4 is considered to be the main hormone produced by the thyroid gland, and with elevated levels in the blood, hyperthyroidism is usually diagnosed, which means increased production by the organ itself or an overdose of medications without a doctor’s prescription.

Thyroxine plays an important role in metabolism. It activates the process of fat breakdown, helps digest carbohydrates, and synthesizes protein. To maintain and regulate normal temperature The body requires the hormone T4. The growth and development of the child depends on it of a certain age as well as education essential vitamins in the liver. It can be safely equated to one of the most important hormones secreted by the endocrine system. It is on this that the basic metabolism, in which energy is released, depends, because even at rest a person needs it. Thanks to it, all human organs work and function. Violation of the level of T4 in the blood threatens with extremely unpleasant consequences.

Why do you need a T4 hormone test?

When a patient comes to the clinic with suspected thyroid dysfunction, tests for TSH and T4 are usually prescribed. Sometimes various combinations are used at the discretion of the specialist. This saves time and money to determine the presence of the disease and reliably reflects the overall picture.

If there are no expressed complaints and the person feels satisfactorily during the initial visit, it is recommended to donate free TSH and T4.

When early stage Graves' disease (diffuse toxic goiter) you should take a blood test only with free T3 and T4. During treatment, hormone levels decrease rapidly, which needs to be monitored. At the same time, the TSH value changes much more slowly, therefore, the analysis of this hormone will not have time to change, like T3 and T4.

If the functioning of the thyroid gland is reduced, thyroxine obtained in the laboratory is recommended to take a blood test for TSH. It is worth noting that taking pills before taking thyroxine is prohibited, otherwise the result will be unreliable. In such a case, the laboratory technician will only determine the amount of hormone that the patient took, since its amount is equal to that found in the body.

Thyroxine changes its value and increases several times during pregnancy. At the same time, TSH tends to decrease due to increased production human chorionic gonadotropin human (hCG). It is located in the placenta and transfers some of the functions of TSH to itself. Pregnant patients are recommended to take a blood test for TSH and free T4 in order to correctly determine their amount; the thyroid hormones TSH and T4 normal during pregnancy should correspond to the gestational age. The T4 norm by trimester differs significantly, this is important to take into account.

The form that came from the laboratory contains the following values:

hormone St. T4 or T3 - stands for free hormones;
in the presence of English letter F means that it was free hormones that were studied.

What is the norm for T4

Determination of the availability rate free thyroxine in the blood depends on the laboratory, research equipment, and the use of high-quality reagents. The results always indicate values that correspond to the norm. T4 is measured in pmol and ranges from 9 to 19. Third generation professional equipment is mainly used.

The correct determination of thyroxine depends on the general condition of the patient. Naturally, during pregnancy, pmol can increase, which is not a pathology or deviation. The values of the general analysis for T4 fluctuate, in contrast to the amount of free thyroxine.

Symptoms and causes of elevated thyroxine in the blood

The reasons may be violations and various pathologies thyroid gland (multinodular or toxic goiter, Graves' disease) or pituitary gland (the appearance of a thyrotropin-secreting adenoma).

The patient often turns to the doctor with concerns related to:

increased sweating without visible reasons;
increased irritability;
constant feeling fatigue even without physical effort;
increased heart rate at rest;
feeling of interruptions in heart rhythm;
increased hand tremors;
sudden weight loss without lifestyle changes.

An increase in the level of thyroxine in the blood affects general condition and human well-being in connection with the release increased energy from fatty deposits. Their reserves begin to decrease, but the energy continues to be released and redirected in the human body. At the same time, the physiological reactions of the body begin to intensify. Thus, normal excitability is replaced by increased irritability, the pulse and heartbeat increase, leading to tachycardia, the fingers begin to tremble, developing into tremor. After some time, the patient loses weight without dieting or increased physical activity, which only worsens well-being and is one of the signs of disorders, and not sudden slimness. This leads to disruption of the functioning of the heart and nervous system. If you are unwilling to ask for help and long-term storage Elevated T4 can cause osteoporosis, which is weakening of the bones, leading to brittleness and fractures.

Causes of low T4 hormone

With insufficient thyroid function or hypothyroidism, there is always a decrease in the level of thyroxine in the blood. In other cases, the reasons may be:

the presence of surgery to remove the thyroid gland in the patient;
inflammation of the thyroid gland (occurrence autoimmune disease leading to sharp decline hormone levels);
overdose medicines if treatment instructions are not followed redundant function against the background of toxic goiter, thyreostatics;
decrease in T4 due to the appointment of treatment with radioactive iodine for a patient with thyrotoxicosis;
the presence of disturbances in the functioning of the pituitary gland.

Signs of a decrease in hormone levels that should alert you may include:

inhibited reactions, drowsiness;
feeling of cold even in a hot room, chilliness;
peeling of the skin, dry mucous membranes;
sudden weight gain for no apparent reason;
decreased heart rate;
pressure surges;
swelling of the limbs;
hoarse or hoarse voice;
constant weakness accompanied by irritability and nervousness.

The importance of the hormone thyroxine during pregnancy

Free T4 plays a huge role for the fetus developing inside the womb. Its amount is responsible for the rate of brain development and maturation of the child’s nervous system in the first trimester. In women, like men, the level of the hormone is not particularly different, but during pregnancy it increases. Doctors do not recommend doing a blood test for thyroxine content, since its value will not reflect the real clinical picture. TSH increases, but in its protein-bound state, thyroxine remains inactive.

If you still need to take a blood test, it is better to determine the level of free T4. There should be no deviation from the norm here. A small amount of increase is acceptable, but not decrease. This can become a threat to the development of the fetus and requires immediate correction and adequate treatment of the thyroid gland to avoid unforeseen complications.

The T4 hormone is less active than T3, but its action is very similar to it. Thus, during analyzes with any deviations, they show an increase and decrease almost simultaneously, with the exception of some temporary cases. TSH and T4 may be elevated due to various reasons, but most of them are related to problematic work adrenal glands

TSH is elevated, T4 is elevated: symptoms

You can understand that a person is beginning to have problems with hormonal levels by preliminary symptoms that do not appear immediately. On initial stages They are the easiest to distinguish, which makes it possible to identify the problem in advance and begin prompt treatment. The main symptoms include the following:

Increased heart rate;
Fatigue, which manifests itself chronically and is not associated with too high stress on the body;
Increased sweating, noticeably higher than before;
Rapid irritability, which affects a person’s behavior;
There may be a sensation of interruptions in the heart area;
Gradual and stable weight loss, provided that the diet and physical activity do not change;
Slight hand tremors.

When TSH decreases and T4 increases, these symptoms can also appear, since their main causative agent is T4.

T4 hormone is higher than normal, what does this mean?

When considering the case when free T4 is higher than normal and what this means, it should be taken into account that the effect of the hormone on the body increases. When TSH is elevated and free T4 is elevated, an increased breakdown of organic substances occurs in the body. This leads to the release of excess energy. Not only energy from incoming food is used, but also from existing fat deposits. The released energy enters various parts of the body, where natural processes. Physiologically natural reactions do not acquire normal level. Thus, excitability develops into irritability. The heartbeat increases, tachycardia appears, which when increased loads creates on the body great danger. Due to the excessive reaction speed of the nerves, tremors and bouncing of the fingers occur.

When TSH is low and T4 is high, weight loss occurs due to fat burning. But this weight loss cannot be called beneficial for the body. This occurs due to disorders of the nervous system and heart function, which becomes dangerous condition. Also, there is no limitation here, which leads to exhaustion of the body. Muscular and bone begins to weaken, the patient develops constant fatigue. The risk of injury increases greatly.

TSH and free T4 are elevated: reasons

Diseases do not appear out of nowhere. If TSH and T4 are elevated, a specialist can explain what this means after the tests. Fluctuations in hormones occur under the influence of external and internal factors and for each of them there is a number of reasons why the increase occurs. The following factors can lead to an increase in T4:

Subacute and acute thyroiditis;
Thyroid dysfunction, which occurs in women after childbirth;
Big excess weight, which puts people with clinical obesity at risk;
Elevated levels of immunoglobulin G in myeloma;
Choriocarcinoma;
Action of the human immunodeficiency virus;
Chronic liver diseases;
Glomerulonephritis, which appears with nephrotic syndrome;
Toxic diffuse goiter;
Porphyria;
The use of synthetic hormonal drugs that are analogues of thyroid hormones, such as methadone, cordarine, insulin, levodopa, iodine-containing x-ray substances, and so on.

Often the patient himself does not know what leads to an increase in T4 levels. There is not always one reason and the matter may lie in several areas at once.

How to lower hormones, TSH and T4 elevated

First of all, experts begin to look for what caused the increase. If you manage to diagnose the disease at an early stage, then it is much easier to recover from it. If you destroy the source of the disease, the hormones will return to normal on their own. If a patient has a tumor, then to solve the problem, experts often recommend removing the part of the organ on which it is located. If you don't produce surgical intervention, then it remains high risk more serious problems arise.

In later stages of diseases, treatment is more complex, not to mention the fact that in some cases full recovery will not be able to achieve. When a patient receives tests where TSH is normal and T4 is elevated, the attending physician understands what this means and what to do about it. But when the diagnosis is made at a late stage of the disease, it may already be too late to treat it. All this is connected not only with complications after operations and other treatments, but also with the possibilities of medicine. In some cases, chronic hypothyroidism develops, which a person will have to put up with throughout his life.

In this form of the disease, as well as in its milder manifestations, one of the best options treatment is taking medication. Most often this hormonal drugs, which will help reduce T4 and other problematic factors. To avoid complications in mild form illness and not to expose the patient to the risk of surgery, then after passing the appropriate tests, medications are prescribed. Here you need to take into account the body’s reaction to the components that make up the medicine, and also do not forget about the dosage so as not to exceed the amount.

Nutrition also becomes additional factor affecting the decrease in hormonal levels. Strong effects It won’t be possible to achieve here, but it will alleviate the situation proper diet quite possible. Experts recommend consuming more raw vegetables, seafood, legumes, grains and low-fat, but protein-rich foods. Everything should be rational and you shouldn’t consume too much of anything. In any case, an individual treatment plan is drawn up for each patient, thanks to which it is possible to overcome the symptoms and causes of the disease in order to return the hormone level to normal.

18 T4 below normal: treatment

When any hormone deviates from the normal level in the body, any manifestations of these consequences immediately begin. When TSH is normal and T4 is lower, this can be found out in advance without tests. This manifests itself through certain symptoms.

TSH and T4 hormones are low: symptoms

Despite the fact that the imbalance does not occur without a trace, the symptoms may not be so pronounced at first, since the body still has the resources to overcome the problem. But after a certain time of struggle, the manifestations come out and the person begins to feel differently. Basically, symptoms appear only after a couple of months and people consult a doctor with a certain delay. The most common symptoms of low free T4 with normal TSH are as follows:

The appearance of chills;
Noticeable memory deterioration over the past few months;
Increased fatigue and muscle weakness;
Problematic condition of nails, hair and skin, which sharply deteriorate from a lack of hormones;
Swelling of the extremities;
Violation of the stability of the menstrual cycle;
Weight gain regardless of diet and activity.

Many of these symptoms turn out to be quite tolerable at first. But when chronic condition, when free T4 is below normal and TSH is normal, it can cause the patient to fall into a coma. Treatment should begin as soon as possible. Patients do not understand what it means: TSH is increased, T4 is decreased, and what degree of deviation it is. It is for this reason that you should completely trust the treatment to doctors and not try to correct the situation yourself.

T4 hormone is below normal: what does it mean. Diagnostics

When a hormone shift to a lower side is detected, this is only one indicator, which is not enough to diagnose the patient. If free T4 is below normal, then what this means is difficult to immediately determine. At this stage, this only means that the patient has problems and the specialist can outline their approximate range. In addition, a general blood test, a test for total thyroxine, biochemical analysis And ultrasonography internal organs. Here you need to determine the size of the thyroid gland in order to continue treatment in the right direction.

Biochemistry is carried out in order to determine the cholesterol level in the blood. This hormone is responsible for the breakdown of cholesterol, so if it increases, it will be seen that T4 has decreased. This additional research to confirm the diagnosis, after which treatment can be prescribed.

T4 below normal: treatment

The body cannot replace this hormone in any way or obtain it from ordinary foods. Thus, if deviations occur, they cannot be dealt with without outside help. Putting it off will only make things worse. the situation and possible death. The main method of treatment is replacement therapy. It is relatively safe and at the same time effective method treatment. In particular, it shows itself well at first, since it does not allow the body to worsen its condition during the period of time when other tests and other studies need to be carried out. The patient is prescribed the required hormones in the missing quantities, which helps to maintain normal health.

If free T4 is below normal in a chronic manner, then replacement therapy may be required for the rest of life. This is relevant provided that there is no way to solve the problem more radically surgically. During replacement therapy, drugs are prescribed that are safe for other organs and support only the endocrine system.

When the minimum threshold of normal is reached, if this was noticed in a timely manner, patients are recommended to undergo iodine therapy. Both foods that contain large amounts of iodine and preparations that contain it are suitable for this. If the hormone does not increase, but continues to decrease, then you should switch to hormone replacement therapy.

T4 is below normal during pregnancy

During pregnancy hormonal background changes often and it has absolutely various manifestations. IN in good condition hormones must change in the required direction, but still fit into the norm for women who have conceived. If free T4 is below normal during pregnancy, this can lead to miscarriage, or the death of mother and child, if nothing is done about it. As a rule, after a certain stage of pregnancy, expectant mothers need to be tested for hormones, so detection of the disease must be timely. As a rule, a substitute is used here hormone therapy. The problem may be that there will be surges in other hormones, so a more precise selection of funds will be required so as not to harm the body. You will also need to monitor the state of hormones throughout the entire pregnancy and the blood must have the normal level of T4 during pregnancy in the 3rd trimester, both before childbirth and during breastfeeding.

To avoid an imbalance of the T4 hormone in the body, you should monitor your diet. The diet must contain foods that contain iodine and protein in order to have the proper level of T4 in the blood of women. They cannot be completely eliminated, so even during diets you need to carefully select foods. Very serious effect on hormones oral contraceptives which are based on hormonal effects on the body. They cause quite a lot of problems, which leads to deterioration of health.

Injuries to the thyroid gland, as well as the head, can lead to a decrease in the hormone. This is temporary or permanent, depending on the complexity of the case. Exhaustive hunger strikes or severe food restrictions can lead to hormonal imbalances due to their insufficiency. Thus, due to a decrease in T4, weight will be gained, regardless of the efforts of the person losing weight. Detection of disorders occurs late due to the fact that changes begin at the cellular level and take time to manifest on a more serious scale.

When contacting an endocrinologist, the patient receives a list necessary examinations, among them tests for T4 and. Thyroid hormones contain iodine, an element involved in metabolic processes.

When diagnosing diseases of the thyroid gland, in addition to T4, the doctor prescribes a blood test for T3, the hormone responsible for oxygen metabolism in tissues.

T4 hormone, thyroxine is responsible for heat exchange, oxygen saturation of tissues, protein metabolism, enhances the production of vitamin A, lowers cholesterol levels and the release of calcium from the body, and has a positive effect on heart function. The concentration of T4 in the blood fluctuates depending on the time of day. The maximum volume of the TSH hormone in the blood occurs in the morning, the minimum in the evening and night. The concentration also depends on the time of year. Thyroxine reaches its maximum level in the autumn-winter period, its minimum in summer period. T4 levels also increase during pregnancy.

What does a T4 blood test include and in what cases is it prescribed?

The analysis includes two indicators: free T4 and total T4 (free and protein-bound hormone). The bulk of thyroxine is present in the blood in bound protein form and only three percent in free form. But free T4 is a more active substance.

symptoms of hypothyroidism;
symptoms of thyrotoxicosis;
goitre;
control after surgery;
use of hormonal contraceptives;
inability to become pregnant and bear a child;
absence of menstruation;
male infertility;
bearing a child;
diffuse toxic goiter;
arrhythmia;
high level prolactin in the patient’s blood;
impotence;
low libido;
hair loss;
weight gain or unexpected weight loss;
inadequacy of emotional states;
depression.

Preparing to take a hormonal test

For achievement qualitative analysis blood test for total and free T4, T3 and TSH, the rules must be followed. A month before donating blood, you must stop taking medications that affect the thyroid gland. A few days before the test, stop taking medications with iodine. Alcohol and cigarettes are prohibited during the testing period.

Blood sampling occurs in the morning on an empty stomach. Boiled water you can drink. Endocrinologists advise spending the morning before submitting the material for analysis in bed, limiting yourself in physical activity.

Decoding hormonal tests

An endocrinologist is reading the test results. Only a specialist can draw the correct conclusion and make a diagnosis if the titers differ from the norm.

Normal values for T4

T4 general for children under one year of age - 69.1-206;
T4 general for younger children school age — 77,2-160,9;
T4 general norm for teenagers - 64.3-141.6;
T4 adult men - 64.3 - 160;
For teenage girls, the T4 norm is 58 – 133;
For women, the T4 norm is 64.3 -160;

Norm for free T4:

Infants - 9.8-23.2;
Toddlers 8.7-16.2;
Children of primary school age 6.7-16.5;
Teenagers 8.4-13.5;
Adults 7.7-14.2.

Titers exceeding the norm suggest the following violations:

myeloma;
obesity;
choriocarcinoma;
certain symptoms in newborns;
liver problems, most often chronic;
resistance to thyroid hormones;
thyrotoxicosis, independent of TSH;
toxic goiter;
thyroiditis in various forms;
disorders of the thyroid gland in women in labor.

Reduced titers of T4 free and T4 total indicate the following problems:

hypothyroidism;
inflammation of the pituitary gland;
Sheehan's syndrome;
autoimmune disorders;

An increase in the level of the total hormone T4 indicates the following problems:

porphyria;
toxic adenoma;
T4-resistant hypothyroidism.

T4 light above normal is observed in the following pathological processes:

drug heparin.

A low free T4 level is possible if the following problems are observed:

drugs (heroin);
sudden weight loss in obese patients;
surgical intervention;
lead contamination;
iodine deficiency;
if the patient abuses a low-protein diet;
Thyrotropinoma.

The following drugs lead to a decrease in free T4:

phenytoin;
carbamazepine;
anabolics;
hormonal contraceptives;
lithium-based drugs;
methadone therapy;
therapy with thyreostatics;
octreotide.

Norm TSH in women bearing a child

Clinical studies of TSH hormone levels are necessary when examining pregnant women, since normal TSH level necessary for proper operation thyroid gland. Significant fluctuations in hormonal levels complicate pregnancy, and there is a risk of miscarriage or the birth of a defective child. Congenital diseases endocrine system lead to impaired mental development, up to cretinism, as well as stunting and physical underdevelopment.

The norm for women carrying a child is 0.1-0.4. TSH levels are lowest in the first few weeks. Patients with are prescribed thyroxine therapy. The problem is detected already at the stage of palpating the thyroid gland; in such cases it is enlarged. Hypothyroidism is especially dangerous in the first trimester.

Causes of primary hypothyroidism during pregnancy

Deviation from the norm and increase Free TSH is justified by the following reasons:

iodine deficiency;
ectopia, dysteginesis, abnormal development of the thyroid gland;
irradiation of the endocrine gland;
use of radioactive iodine in the treatment regimen;
excess iodine when taken for a long time;
oncology;
thyroidectomy;
autoimmune thyroiditis;
postpartum thyroiditis;

Along with other hormones, T4 performs the most important function both in individual cells and in the human body as a whole - regulation of metabolism, basal metabolism, metabolic rate of all physiological processes.

The main thyroid hormones - TSH, T3, T4 maintain the body's energy balance and control synthetic processes biologically active substances, also ensure normal levels of iodine in the blood. Under the influence of hormones, protein catabolism occurs, T4 is responsible for this. This means that in case of malfunctions endocrine organ there is a decrease or increase in the level of the hormone in the blood.

Certain disorders hormonal system, as a rule, are expressed by specific symptoms and require laboratory research to adjust therapy.

Let's take a closer look at what the T4 hormone is, its types and standard values in human blood.

Hormone thyroxine (T4)

Description

Thyroxine is a thyroid hormone (T4), consisting of four iodine atoms and two amino acid residues. The hormone got its name because chemical structure, and is often called tetraiodothyronine. The T4 hormone has a simple structure and can be created artificially.

Biochemically, thyrocytes capture iodine from the body by follicle cells, preserving it in the form that precedes the hormone - thyroglobulin. When the thyroid gland malfunctions, the finished hormone in pure form is released into the blood. Tetraiodothyronine is quite active hormone, as a result high content a person almost always experiences irritability, tachycardia, long-term use weight loss.

In the blood, T4 binds to protein substrates that perform transport function. That is, the protein - thyroxine-binding globulin delivers the hormone to various cells body. A hormone not bound to globulin is called “free”. The free T4 hormone in this form is contained significantly less than in the bound form.

Symptoms of low T4 levels:

Low blood pressure;
Emotional lability;
Drowsiness;
Weight gain;
Hair loss;
Menstrual irregularities;
Dry skin;
Chilliness.

Symptoms of high T4 levels:

Exophthalmos (protrusion of the eyeballs);
Increased heart rate;
Skin redness,
Tremor of the limbs;
Sweating;
Sleep disturbance.

Laboratory blood test T4

The widespread practice of endocrinologists has included testing for thyroid hormones in each case of complaints about the corresponding symptoms. A blood test for the hormones TSH and T4, T3 is prescribed if hypo- or hyperthyroidism is suspected. For some diseases, hormones are studied in various combinations, for example, T3 and T4 or TSH and T4, TPO, and so on. One of these diseases is Graves' disease, in this case, while taking medicines TSH hormone will not indicate true picture diseases, therefore the level of the T3 hormone and the free T4 hormone in the blood is examined.

When is it appointed?

Research is prescribed in the following situations:

In some cases of medical examination (for example, when registering a patient in medical institutions), during preventive studies;
If you suspect hypothyroidism or if symptoms characteristic of this disease appear;
If hyperthyroidism is suspected or symptoms appear;
To examine infants born to mothers with thyroid diseases;
Pregnant women with thyroid diseases or those predisposed to endocrine system disorders;
After treatment of thyroid diseases and to monitor the effectiveness of therapy.

Rules for taking a blood test for T4

An endocrinologist often informs you how to properly take a T4 test on the eve of a visit to the laboratory. To obtain reliable data and correctly interpret the results, it is necessary to prepare for the study. An analysis for the T4 hormone, like a number of other tests, is taken on an empty stomach, early in the morning and in full emotional and calm state person. Also, there are some nuances that are discussed below.

How to take a T4 test correctly:

A blood test for T4 is taken in the morning, at 8-10 o'clock. This is due to the physiological activity of hormones in the morning. Blood for T4 hormone, free of proteins, taken in the morning shows the most reliable results during laboratory research.

Stop taking other medications in advance, such as oral contraceptives, corticosteroids, NSAIDs or directly hormonal drugs for the treatment of the thyroid gland.
The blood test for T4 must be taken on an empty stomach; eating is prohibited 12 hours before the test.

However, even if all the rules for donating blood for research are followed, there are other reasons for an increased or decreased T4 value.

Norm of T4 hormone

Elevated free T4 against the background of a healthy thyroid gland will indicate pregnancy. Also, in older people, the T4 norm may vary, but will be determined within the boundaries of standard standards. The T4 hormone, the norm of which has fairly wide limits, can be distorted as a result of equipment malfunction and errors in the data obtained.

The table shows the normative values of the T4 hormone in the blood according to age

Analysis transcript

Deciphering the analysis requires a qualified approach and can only be done by specialists. Interpretation of tests occurs after a thorough assessment of the patient being studied, accompanying pathologies, specific medical history (taking medications that affect the level of the T4 hormone).

Free T4 is tested in any accredited laboratory.

Studies are prescribed before and after surgical interventions on the thyroid gland, after hormonal treatment, in case of infertility, to establish various diseases. T4 analysis is indicated for children with increased mental stress, for preventive adjustment of iodine levels in the body.

Free T4 hormone is taken into account in other diseases of the endocrine system, in professional athletes, as well as for indicators of men's health.

Treatment of diseases of the endocrine system, in particular the thyroid gland, is prescribed only by an endocrinologist. Usually, in order to reduce elevated T4, thyreostatics are recommended. If the T4 level is insufficient, replacement therapy is prescribed, which requires long-term use.

Whenever specific symptoms indicating thyroid disease, you should immediately contact a specialist for further medical examination.

T4 levels are above normal

Elevated levels of the hormone in the blood are the result of the following diseases:

Thyroiditis always causes high T4 levels;
Diffuse toxic goiter;
Tumor diseases of the thyroid gland, as a rule, cause the highest levels of the hormone in the blood;
T4 reaches an increased value in obesity;
TSH—independent thyrotoxicosis;
Chronic liver diseases;
Kidney diseases;
Postpartum thyroid dysfunction;
Therapy with drugs containing heparin is characterized by an increased level of T4 in the blood;

Free T4 in pregnant women

T4 will be higher than normal in the first trimester of pregnancy up to 13 weeks, and the norm is 12.0-19.5 pmol/l.

In the second trimester of pregnancy, free T4 will be slightly reduced and amount to 9.6-17.0 pmol/l.

In the third trimester of pregnancy it is low relative to the second trimester and amounts to 8.5 - 15.5 pmol/l.

T4 levels are below normal

Free T4 is reduced in a number of diseases:

Hypothyroidism;
Autoimmune thyroiditis;
Reduced T4 in endemic goiter;
Secondary hypothyroidism;
Insufficient human iodine intake;
Insufficient protein intake (protein wasting);
Thyrotropinoma;
Diseases of the pituitary gland and hypothalamus;
Lead poisoning;
Injecting drug use;
Use of oral contraceptives;
Consequences of radioactive iodine therapy.
After thyroid surgery, T4 may also be low.

Deviations from the normative values of the T4 hormone can occur when using medications. Thus, aspirin, propranolol, furosemide, tamoxifen, levothyroxine and others can increase the level of T4 in the blood, and the level of other thyroid hormones also increases.

T4 may be reduced when used anabolic drugs, carbamazepine, clofibrate, methadone, lithium drugs, octreotide and others.