Thyroxine free (T4 free). Hormonal norm of TSH and T4 free in the human body

The name "hormones" comes from the Greek hormao, which means "to excite" or "to set in motion." These biologically active substances have different chemical nature. It is thanks to the hormones that are produced by the organs of internal secretion that the regulation of metabolism and the implementation of the physiological functions of the body occur.

Several dozens of active substances produced by the endocrine glands and having hormonal activity have been studied. Among them is T4, synthesized by the thyroid gland. It is also called tetraiodothyronine or thyroxine.

The main function of T4 is the acceleration of dissimilation, that is, the processes of energy metabolism (catabolism). It is the normal content of thyroxine that contributes to:

• maintaining the tone of the nervous system;
• adequate metabolism;
• normal functioning of the heart muscle and optimal heart rate.

Finding the hormone T4 in the blood

T4 molecules are born in the thyroid follicles of the thyroid gland. In part, they are enticed by a specific protein that carries out transportation, thyroxine-binding globulin (TSG). It delivers T4 hormones to all corners of the human body.

A small amount of tetraiodothyronine remains in an unbound state. It is called free T4 hormone. It is he who guarantees the biological effect on the body and its results. The concentration of thyroxine in the blood reflects the degree of functioning of the thyroid gland. Therefore, the content of the hormone is crucial in order to determine the presence or absence of pathologies of this endocrine gland.

The norm of the hormone T4 in women

In the morning, women are characterized by the highest level of T4. After the onset of noon, it gradually decreases and at night falls to a minimum.

A similar situation is observed at different times of the year. With the onset of October and until the end of March, the concentration of T4 in the blood of the fair sex is maximum. In the summer months, it decreases significantly.

Normal indicators of tetraiodothyronine are as follows:

During the period of bearing a child in the hormonal background of a woman, changes are inevitable.

The amount of total thyroxine increases significantly and is (pmol / l):

• minimum - 75.0;
• maximum - 230.0.

Regarding free T4, its permissible content increases in the first trimester, and then gradually decreases:

The release of the amount of free thyroxine beyond the norm can negatively affect the bearing of the baby, and the outcome of pregnancy, and even the condition of the born crumbs. Therefore, it is necessary to constantly monitor the level of hormones and promptly correct any unwanted deviations.

It should be borne in mind that if a woman has a pathology of the organs of the endocrine system, then the probability of pregnancy drops sharply. Very often, such ailments violate the reproductive function and provoke infertility.
Timely therapy will eliminate such problems.

The level of thyroxin in a healthy female body remains almost unchanged for many years. Its rate only slightly decreases closer to menopause. This is due to the inevitable restructuring of the body and its adaptation to somewhat changed conditions.

In mature and advanced age, the content of free T4 in female blood is from 8.0 to 18.0 pmol / liter.

Hormone T4: the norm in men

The normal content of total thyroxine in male blood is slightly higher than in female blood. In an adult representative of the stronger sex, the level of the hormone T4 is as follows (pmol / l):

• minimum - 64.3;
• maximum - 160.0.

Free T4 should be in the range of 10.1 to 23.0 pmol/L. That is, its upper value is slightly higher than the norm for women.

After reaching adulthood, total thyroxine can decrease to 129, and free - up to 18 pmol / l without negative consequences for the body.

Hormone T4: the norm in children

A newborn baby produces more thyroxine than adults, and therefore its norm is higher. The amount of free hormone should be from 22.0 to 49.0, and total - 120.0-250.0 pmol / liter.

In adolescence, the content of thyroxin in the blood is approximately the same as in adults of the corresponding sex.

Exceeding the T4 norm

Symptoms

An increase in the T4 hormone compared to the established norm is accompanied by symptoms such as:

• excessive sweating, especially during sleep. At the same time, not heat is felt, but cold;
• unreasonable irritability, which is impossible to cope with;
• fatigue even with minor mental or physical exertion;
• rapid heartbeat;
• trembling of the hands;
• weight loss without changing lifestyle, without additional effort;
• the feeling that the heart periodically stops beating and seems to freeze.

With an increase in the hormone T4, there is an accelerated breakdown of energy substances and the release of additional energy. It goes to various parts of the body and distorts the usual physiological reactions, turning them into too violent and completely unacceptable. For example, a calm state is replaced by irritability, a moderate heartbeat is replaced by tachycardia, the usual rate of nervous reaction becomes too high, and the hands begin to twitch.

This position provokes weight loss. But it cannot be called natural and desirable, since the causes are violations of the normal functioning of the heart muscle and nervous system.

If this condition is not changed and the T4 hormone is not returned to normal, then bone tissue weakening and osteoporosis will soon occur, which will inevitably end in fractures.

The reasons

When the level of total T4 rises, the patient can be suspected of:

• toxic adenoma;
• thyrotropinoma, although its probability is very low;
• T4-resistant hypothyroidism;
• HIV infection.

The excess value of free thyroxine is possible in such cases:

• thyrotoxic adenoma.
• Treatment with heparin.

An increase in thyroxin, both total and free, can be caused by:

• Overweight.
• Chronic hepatic ailments.
• Syndrome of resistance to thyroid hormones.
• nephrotic syndrome.
• Myeloma with high specific gravity of IgG.
• Toxic goiter.
• Choriocarcinoma.
• Postpartum thyroid dysfunction.
• TSH-independent thyrotoxicosis.
• Familial dysalbuminemic hyperthyroxinemia.

Hormone T4 below normal

A decrease in T4 levels below the optimal level leads to insufficient thyroid function - hypothyroidism. It manifests itself with such possible symptoms:

• rapid and unreasonable weight gain;
• dry skin;
• cold intolerance;
• violation of the menstrual cycle;
• puffiness, especially in the morning and as evening approaches;
• hair loss, up to rapid baldness (in men).

In childhood, a lack of a hormone is dangerous because there is a high probability of a delay in physical and mental development.

Hypothyroidism happens:

• Primary, congenital or acquired, appeared due to the presence of:
  • endemic goiter;
  • inflammation of the thyroid gland: autoimmune thyroiditis. The consequence of its development is an insufficient amount of the hormone T4;
  • surgical removal of the thyroid gland.
• Secondary:
  • neuroendocrine disorder - Sheehan's syndrome;
  • pathological process in the pituitary gland.
• Tertiary:
  • skull and head injuries;
  • inflammation in the hypothalamus.

In addition, the causes of hypothyroidism can be:

• An overdose of drugs used to treat excessive thyroid function in the presence of toxic goiter.
• The consequences of the use of radioactive iodine, which was used for the treatment of thyrotoxicosis.
• Compliance with an uncontrolled diet, poor in proteins and iodine.
• Contact with lead.
• Addiction to drugs, in particular, to heroin.
• Significant and too rapid weight loss in obese people.

How to get the correct T4 test result

The material for determining the content of the hormone T4 is venous blood. In order for the results of the analysis to be as correct as possible, it is necessary:

• at least three days before the procedure, do not use drugs that contain iodine;
• give up medicines containing thyroid hormones for a month;
• for a day to avoid intensive sports;
• avoid stress and psychological overload;
• Do not smoke or drink strong drinks the day before.

You can drink pure non-carbonated water. Immediately before blood sampling, it is necessary to bring the nerves to a state of rest and sit quietly for half an hour. If several procedures are prescribed, then the blood must be donated first.

The sampling of material for analysis is carried out in the morning and on an empty stomach. To avoid subjective errors, it is desirable to carry out the procedure twice and, if possible, in different laboratories.

It is necessary to determine the level of thyroxine, as well as other hormones, during the annual preventive examination. If a person has thyroid diseases, then such a procedure should be carried out quarterly. This will help to control the situation, undergo therapy on time and lead a normal life without reducing its quality.

The term “hormones” (in Greek ὁρμάω) literally translates as “I stimulate”, that is, these are substances that are produced by special groups of cells (glands), transported to other groups of cells and intended for stimulation in the last certain processes.

Hormone T4 (thyroxinum, thyroxine, tetraiodothyronine) is a thyroid hormone (that is, produced by the thyroid gland), is synthesized from iodine and essential amino acids, contains 4 iodine atoms and stimulates metabolic processes in the body. It affects the work of almost all organs and systems, so it is very important to understand the consequences of its deficiency or excess.

T4 hormone: its role in the body and its presence in the blood

In more detail, the role of T4 in the human body is as follows:

1. Ensures the normal functioning of the heart.
2. Promotes the functioning of the liver.
3. Reduces deposits of cholesterol on the walls of blood vessels.
4. Ensures the production of heat by the body.
5. Affects the maturation of eggs and the formation of mucous membranes on the genitals in women.
6. Affects the weight of a person.
7. Accelerates the metabolism of proteins.
8. Promotes the metabolism of fats.
9. Provides cells with oxygen.
10. Affects the psyche.
11. Necessary for the production of triiodothyronine (thyroid hormone T3).

Did you know? The annual turnover of iodine in the world is about 25 thousand tonshe N.

Transportation of thyroxine to the organs is carried out through the blood. To do this, it mainly attaches to special proteins (TSG - thyroxin-binding globulin, transthyretin and albumin). This hormone is called T4 bound.

A small part of the hormone (about 0.1%) is transported independently, without binding to proteins. In this case, it is called free T4 (FT4) and has a stronger effect. In a free state, the hormone helps the heart to beat, the lungs to breathe, the intestines to move food, the brain to work, and the kidneys to form urine. This hormone does not affect only the senses, speech, sensations, emotions, the spleen, the production of spermatozoa and male sex hormones.

The bound and free parts together form T4 total.

The rate of the indicator

The analysis is carried out for the content of free and total thyroxine in the blood, but the first gives more information about the patient's health status. Hormone levels are different for women, men and children.

Among women

For women, the normal levels of the hormone are:

1. General: 54.0 - 156.0 nmol / l.
2. Free: 10.5 - 22.0 pmol/l.

1. General: 75.0 - 230.0 nmol/l.
2. Free: 7.6 - 18.6 pmol / l.

• : 12.0 - 19.6 pmol/l;
• : 9.7 - 17.0 pmol/l;
• : 8.5 - 15.6 pmol / l.

In men

The norm of the indicator values ​​​​for men varies in the following range:

1. General: 65.6 - 181.5 nmol / l.
2. Free: 12.0 - 21.9 pmol / l.

In children

The norms of general T4 for children are as follows:

1. Up to 1 year: 124.9 - 245.9 nmol / l.
2. From 1 to 6 years: 118.4 - 194.4 nmol / l.
3. From 7 to 12 years: 97.8 - 176.3 nmol / l.
4. From 13 to 17 years: 82.4 - 172.5 nmol / l.

1. Up to 1 year: 14.5 - 25.7 pmol / l.
2. From 1 to 6 years: 11.6 - 21.9 pmol / l.
3. From 7 to 12 years: 14.5 - 21.9 pmol / l.
4. From 13 to 17 years: 14.5 - 23.2 pmol / l.

Causes and symptoms of a decrease in the level of T4 hormone

Reasons for low hormone levels include:

1. Treatment of the consequences of poisoning with an excess of secreted hormones.
2. Hashimoto's thyroiditis (autoimmune), when, under the influence of unexplained factors, the immune system produces antibodies against thyroid cells, due to which their function decreases.
3. Surgery to remove the thyroid gland.
4. Sheehan's syndrome is a complication after childbirth, as a result of which the supply of oxygen to the pituitary gland deteriorates.
5. Other diseases of the pituitary and hypothalamus.
6. An overgrowth of the thyroid gland due to iodine deficiency (endemic goiter).
7. Skull trauma, brain injury.
8. Deterioration of the thyroid gland (hypothyroidism).
9. Lack of ingestion of iodine and proteins (extreme diets).
10. Lead poisoning.
11. An error occurred while running the study.
12. Taking certain medications.

Did you know? Forensic experts use iodine to find fingerprints on paper.

The intake of such drugs leads to a reduced level of free T4:

• sulfonamides;
• amiodarone;
• ranitidine;
• glucocorticoids;
• penicillins;
• anticonvulsants;
• reserpine;
• potassium iodide;
• anabolic steroid;
• thyreostatics.

• glucocorticoids;
• penicillins;
• sulfonamides;
• iodides;
• triiodothyronine;
• itraconazole;
• valproic acid;
• co-trimoxazole;
• cholestyramine;
• primidone;
• carbamazepine;
• ketoconazole;
• phenobarbital;
• stanozolol;
• clofibrate;
• corticotropin;
• phenytoin;
• phenylbutazone;
• lovastatin;
• lithium salts;
• drugs for breast cancer;
• methimazole;
• sulfonylurea derivatives;
• furosemide;
• asparaginase;
• drugs against.

• chronic fatigue;
• decreased ability to think analytically;
• weight gain;
• low body temperature;
• problems in the work of the intestines;
• violation of the heart rhythm;
• dry skin;
• brittle nails;
• irregular menstrual cycle;
• edema;
• hair loss;
• susceptibility to low air temperature.

Important! In the absence of treatment for a low T4 level for a long time, a person can fall into a thyroid coma and die.

Causes and symptoms of increased T4 hormone levels

The following reasons lead to an increased content of thyroxine in the blood:

1. Myeloma.
2. Excess weight.
3. Damage to the vessels in the kidneys.
4. Postpartum complication in the form of activation of the immune system to destroy thyroid cells.
5. Thyroiditis is inflammation of the thyroid gland.
6. A tumor in the female genital organs.
7. Hyperthyroidism is an increase in the intensity of the functioning of the thyroid gland.
8. Hepatosis, porphyria, cirrhosis of the liver.
9. Stress, physical activity.
10. Excess ingestion of iodine.
11. Taking certain medications.

To exceed the norms of free thyroxine leads to the following medications:

• aspirin;
• erythropoietin;
• radiological contrast agents;
• imidazole;
• amiodarone;
• heparin;
• propranolol;
• carbamazepine;
• furosemide;
• oral contraceptives;
• L-thyroxine.

• thyrotropin;
• methadone;
• tamoxifen;
• fluorouracil;
• thyreoliberin;
• synthetic;
• prostaglandins;
• insulin;
• levodopa;
• phenothiazine;
• propylthiouracil.

Excess thyroxine is manifested by such symptoms:

• heavy sweating;
• constant feeling of fatigue;
• nervousness;
• accelerated heartbeat;
• violation of the heart rhythm;
• sudden weight loss;
• trembling of hands and feet;
• bulging eyes;
• intolerance to high air temperature.

Important! During pregnancy, T4 may increase - this does not require treatment, a decrease in its level is a danger to the development of the fetus.

Effects

The lack of thyroxine causes the following consequences:

1. Enlargement of the thyroid gland.
2. Myxedema - severe swelling of the face, arms, legs.
3. Decline in intellectual abilities.
4. In children - a lag in physical parameters, mental retardation.
5. Inability to conceive in women.
6. Drop in blood pressure.
7. Pregnant women have fetal malformations.
8. Thyroid coma, death.

1. Thyrotoxicosis, Perry's disease, Graves' disease, Flayani's disease, diffuse toxic goiter, Graves' disease - poisoning of the body with excess thyroid hormones.
2. Washing out of calcium, increasing the susceptibility to fractures.
3. Heart failure.
4. Insomnia, anxiety.
5. Thyrotoxic coma, death.

Indications for analysis

An analysis of the level of free thyroxine is carried out in order to:

• assess the performance of thyroid functions;
• control hormonal treatment of the thyroid gland;
• establish the presence of a goiter (enlarged thyroid gland).

• diagnosis of hyperthyroidism or hypothyroidism;
• to control the result of artificial suppression of TSH (thyroid-stimulating hormone).

Important! This hormone is produced under the influence of thyroid-stimulating hormone (TSH), which is produced by the pituitary gland (a part of the brain) and affects the production of T3. An excess of TSH inhibits the production of thyroxine and vice versa, therefore, during the initial treatment, it is advisable to donate blood for the presence of TSH, T3, T4.

The reason for the appointment of a blood test for the content of thyroxine may be:

1. Pregnancy.
2. Problems with conception.
3. The presence of patient complaints, the assumption of abnormal functioning of the thyroid gland.
4. Developmental problems in children.
5. Diseases of the pituitary gland.
6. Heart diseases.
7. The presence of excess cholesterol in the blood.
8. Prevention of thyroid diseases.

Analyzes: how to prepare and which doctor to do

An analysis for thyroid hormones can be taken at an endocrinological dispensary, a private laboratory or a public medical institution, provided that the appropriate reagents are available there. The referral for analysis is given by an endocrinologist, and in case of relevant complaints to other specialists, a cardiologist, gynecologist, therapist, pediatrician and other specialists.

For analysis, venous blood is needed.

Did you know? During a lifetime, a person needs 1 teaspoon of iodine for the normal functioning of the thyroid gland..

To avoid distortions in the results, it is important to follow the rules for preparing for testing:

1. Do not eat anything 12 hours before donating blood. You can drink still water.
2. Take the test in the interval from 8.00 to 12.00, when the body produces the most thyroxine.
3. Before donating blood, do not drink medicines and do not take x-rays. Some medications need to be canceled a few days before the analysis or laboratory assistants should be warned about their intake.
4. The day before the analysis, do not drink alcohol, do not play sports, avoid stressful factors, limit smoking if possible.
5. To pass the analysis, for women, the 6-7th day of the menstrual cycle is best suited.

Deciphering the analysis

The final diagnosis is made on the results of the analysis of not only T4, but also TSH, T3, the presence of antibodies to thyroid thyroperoxidase (AT TPO), ultrasound of the thyroid gland.

The following options are possible:

1. Low T4, high T3 with an increase in TSH and AT TPO - autoimmune thyroiditis.
2. Very low T4 with very high T3 and TSH - diffuse toxic goiter.
3. Increased T4 - hyperthyroidism, liver disease, pregnancy, obesity, stress.
4. Decreased T4 - hypothyroidism, diseases of the kidneys, pituitary gland, gastrointestinal tract, iodine and protein deficiency.

Important! Interpretation of the results of the T4 analysis should be carried out only by an endocrinologist.

So, we found out that thyroxine is one of the most important hormones for our body, which determines the correct functioning of all organ systems, therefore, periodic monitoring of its level in order to prevent thyroid diseases is of great importance. To do this, it is recommended to periodically donate blood to analyze the level of thyroid hormones, eat food rich in iodine, and spend more time in the sun.

Tetraiodothyronine, or T4, is a hormone synthesized by the human thyroid gland and performs important functions for the body. However, in some situations, its concentration may deviate from the norm in one direction or another, which is a serious wake-up call. To avoid health-threatening consequences, each person should know what it means if the T4 hormone is elevated, and how to bring it back to normal.

The main causes of an excess of tetraiodothyronine

To begin with, let's figure out what it means if free thyroxine is elevated. It should be noted that not always a deviation from normal indicators indicates serious health problems. In some categories of patients, the level of this substance may be slightly higher, in others it may be lower, and this is due to the individual characteristics of the organism.

But often, if free thyroxine is elevated, this indicates a violation of the thyroid gland. If the situation is not responded to in time, the pathological process can affect other internal organs and systems. Then getting rid of the problem will be much harder.

So, if the free T4 hormone is elevated, this may indicate:

• the development of autoimmune diseases;
• deficiency of iodine, iron or other minerals;
• dysfunctions of the adrenal glands;
• an increase in the hormone prolactin during breastfeeding;
• infectious diseases of various etiology and severity.

However, if free T4 is elevated and GGT is normal, this may also be due to:

• adherence to a diet with the use of a large amount of soy products;
• unfavorable heredity;
• chronic fatigue;
• frequent and severe stress;
• abuse of coffee and alcohol;
• chronic alcoholism.

In addition, one of the reasons that free T4 is increased may be living in an environmentally polluted environment, as well as working at "harmful" enterprises. For example, with the systematic intake of bromine in large quantities, the concentration of a substance can increase so much that a person may well develop thyrotoxicosis.

The use of medications and an increase in T4 in pregnant women

If T4 is elevated with normal TSH during hormone therapy, we can say that this is a common occurrence. Of course, it cannot be called normal, but it should not be considered dangerous to the life or health of the patient either.

So, high free T4 can be the result of hormone therapy in the treatment of various thyroid pathologies, as well as in the abuse of hormonal contraceptives. But other medications can also provoke a jump in the level of tetraiodothyronine, so only the attending physician should conduct therapy and control it.

T4 in expectant mothers

What does it mean if free T4 is elevated in pregnant women? If such a deviation is observed in the first trimester, then the experience is in vain: this is a completely natural phenomenon caused by hormonal changes in the body. After all, not only the uterus, ovaries and mammary glands react to the development of a new life in the mother's tummy, but also the endocrine system, in particular, the thyroid gland. As the fetus grows, the level of tetraiodothyronine will decrease, and, eventually, will become minimal in the last months.

But if T4 is elevated during late pregnancy, this may indicate thyrotoxicosis - excessive production of thyroid hormones by the thyroid gland. Such a deviation occurs with a powerful hormonal failure, preeclampsia and other diseases that often develop in expectant mothers, because their body during this period is not as well protected as it was before pregnancy.

Symptoms of elevated T4

If the T4 hormone is elevated, the body reacts quite sharply to such a deviation. Symptoms of an excess of tetraiodothyronine are manifested through the occurrence of:

• hyperhidrosis (excessive sweating);
• rapid fatigue, loss of strength;
• atrial fibrillation;
• rapid heartbeat;
• trembling in the upper limbs;
• drastic weight loss.

If free T4 is elevated, there is an increased breakdown of body fat, which leads to the release of more energy than with a normal level of this substance. This results in:

• increase in the intensity of heart contractions;
• increased muscular and nervous excitability;
• violation of the normal metabolism in the body.

If such deviations are not responded to in a timely manner, the existing problem will not be solved. On the contrary, elevated free T4 can cause serious malfunctions in the body, which subsequently lead to serious complications.

When is analysis needed?

A biochemical blood test, if free thyroxine T4 is elevated, is necessary with severe symptoms of thyrotoxicosis. Also, a wake-up call and an impetus for contacting an endocrinologist should be frequent unreasonable attacks of arrhythmia, accompanied by shortness of breath, rapid heart rate, chest pain.

However, not only an increased concentration of tetraiodothyronine is an indication for biochemical analysis. A low level of this substance also requires increased attention, since it affects all processes in the body without exception, and can cause the development of serious anomalies.

Is it possible to reduce T4 folk remedies?

Treatment of elevated free T4 with folk remedies gives good results if the cause of the anomaly is not related to any serious pathologies. One of the most effective medicines is the following decoction.

In equal proportions, it is necessary to mix dried and well-chopped roots of elecampane, rhizome of the soulberry, rowan fruits, birch buds and St. John's wort. Place all the ingredients in 1 container, then brew with boiling water in a half-liter thermos. Leave for 2 hours, then filter and take 100 ml of infusion in the morning and evening.

You need to drink the medicine until the level of tetraiodothyronine reaches normal levels. But if the remedy does not help, it means that the cause of the ailment is more serious and requires immediate medical attention.

T4 (thyroxine, tetraiodothyronine) is a thyroid hormone that affects thermoregulation and metabolic processes. In the body of a woman, the normal content of T4 up to 40 years is slightly higher than in men. After the onset of menopause, the concentration of the hormone in the blood decreases and reaches the same level as the males. An increase or decrease in the content of thyroxine in the blood indicates a disease of the thyroid gland or other internal organs. A physiological increase in the concentration of the hormone in women is recorded in the first trimester of pregnancy and a decrease in the last, which is considered to be the norm.

T4 in a woman's body

Thyroxine is synthesized in the follicles of the thyroid gland under the influence of TSH (thyroid-stimulating hormone). TSH is secreted by the pituitary gland and controls the endocrine activity of the thyroid gland. Under the action of the pituitary hormone in the thyroid follicles, 4 molecules of iodine are attached to the thyroglobulin protein - tetraiodothyronine is formed, in other words, thyroxine. Violation of the central nervous system (CNS) leads to a change in the hormonal background in a woman's body, primarily from the thyroid gland.

Synthesized thyroxine enters the bloodstream and binds to transport proteins. In a bound state, the hormone does not affect metabolism. The inactive form of T4 is 99.5% of the total concentration of thyroxine in the peripheral blood. Only a small part of the hormone - 0.5% is able to influence metabolism, thermoregulation, the functioning of internal organs and the central nervous system. The active part of thyroxin is called free T4, the total content of the hormone is called total T4.

Thyroxin in a free state is carried by the blood throughout the body and has an active effect on target cells that are located in almost every organ. Physiological fluctuations in hormone levels depend on the time of day and seasonality. The highest concentration of thyroxine in the blood of a woman is determined in the morning hours before noon, the lowest - at night after midnight. In the warm and sunny season (spring-summer), the content of T4 in the blood decreases, on cold and cloudy days (autumn-winter) it increases. During pregnancy, slight fluctuations in the level of the hormone is considered a physiological norm.

Thyroxine functions:

• activates the work of the central nervous system;
• normalizes the function of the cardiovascular system;
• restores the synthesis of vitamins and amino acids in the liver;
• improves heat production processes;
• has a positive effect on tissue respiration, prevents the process of hypoxia (lack of oxygen);
• helps to strengthen bone tissue;
• reduces the concentration of "bad" cholesterol in the blood, increases the content of the "useful" fraction of total cholesterol;
• normalizes the rate of metabolic processes of proteins, carbohydrates, fats;
• affects the functioning of the endocrine glands;
• supports reproductive function during the fertile period of a woman's life;
• regulates body weight;
• maintains a positive emotional background, controls mood and intellectual activity.

A change in the normal concentration of thyroxin, both up and down, causes serious disorders in the organs and functional systems of the body.

The norm of T4 in the blood of women

To detect changes in the normal concentration of thyroxine in the blood, a laboratory analysis is performed. The study includes determining the concentration of T4, TSH and another thyroid hormone - T3 (triiodothyronine). A comprehensive examination allows you to make the correct diagnosis and correctly interpret the results of the analysis. An ultrasound examination (ultrasound) is additionally performed to identify the state of the thyroid tissues.

For examination, venous blood is taken after a night's sleep on an empty stomach. Refraining from eating should be at least 8-10 hours. A month before the collection of biomaterial, it is necessary to stop taking thyroid hormones. A week before the analysis, in agreement with the doctor, stop treatment with iodine preparations. On the eve of the examination, it is recommended to stop drinking alcohol, eating fatty and spicy foods. One hour before the analysis, you should not smoke. Compliance with the conditions of preparation for diagnosis increases the effectiveness of the study.

Normal T4 levels in the blood in women:

• T4 total - 71-143 nmol / l;
• T4 free - 10-22 pmol / l;
• pregnancy up to 12 weeks T4 free - 12-19.5 pmol / l;
• pregnancy 13-28 weeks T4 free - 9.6-17 pmol / l;
• pregnancy from 29 weeks to delivery T4 free - 8.5-15.6 pmol / l.

As a woman ages, T4 hormone levels may change.

Table: The rate of free T4 in the blood in women, depending on age, µmol / l

Slight fluctuations in the level of thyroxine in the blood of women during the period of gestation is considered a normal course of pregnancy. Exceeding these indicators requires additional diagnostics and therapy. Repeated examinations must be carried out in the same laboratory. The method of determining hormones affects the result of the diagnosis. Different laboratories may give different results, which will be difficult to compare and make a clinical conclusion.

Causes and symptoms of an increase in T4 in a woman's blood

Hyperfunction of the thyroid gland leads to an increased synthesis of thyroxine and the accumulation of large amounts of total and free T4 in the blood. This disrupts metabolism, thermoregulation and the functioning of internal organs. An increase in the concentration of thyroxine in the peripheral blood is accompanied by a decrease in the level of TSH. The pituitary gland compensatory suppresses the synthesis of tetraiodyronine at a high content of T4 and slows down the production of its own hormone.

Reasons for increasing T4 in the blood:

• diffuse toxic goiter (Graves' disease);
• thyrotoxic adenoma;
• choriocarcinoma;
• thyrotoxicosis TSH-independent;
• thyroid dysfunction in the postpartum period;
• obesity;
• nephrotic syndrome;
• severe liver damage (hepatitis, cirrhosis, hepatosis);
• taking medications (thyroid hormones, estrogens, oral contraceptives, aspirin, insulin, furosemide);
• early pregnancy.

Increased synthesis of thyroid hormones causes a characteristic clinical picture:

• irritability, anxiety, nervousness;
• sleep disturbance, insomnia;
• increased sweating;
• subfebrile temperature (up to 38 degrees);
• increased appetite;
• protrusion of the eyeballs;
• tremor of fingers;
• weight loss
• muscle cramps;
• increased heart rate at rest (tachycardia);
• violation of the menstrual cycle;
• infertility.

Untimely access to a doctor leads to the progression of the disease, worsens the prognosis for recovery and life.

Causes and symptoms of a decrease in T4 in women

Hypofunction of the thyroid gland is accompanied by a decrease in the production of thyroxine. Against the background of insufficient T4 synthesis, the pituitary gland is activated and the concentration of TSH in the peripheral blood increases. The compensatory mechanism on the part of the central nervous system normalizes the functioning of the thyroid gland for some time and restrains clinical manifestations. The progression of the pathological process depletes the endocrine function of the pituitary gland, which leads to the appearance of symptoms of hypothyroidism.

Reasons for lowering T4:

• hypothyroidism;
• iodine deficiency in water and food;
• endemic goiter;
• autoimmune Hashimoto's thyroiditis;
• complication after resection (partial removal) of the thyroid gland;
• poisoning of the body with lead and other heavy metals;
• taking medications (anabolic hormones, antithyroid drugs, glucocorticoids);
• benign thyroid tumors;
• disruption of the pituitary gland;
• starvation, sudden weight loss;
• late pregnancy.

With starvation and exhaustion of the body, the content of transport proteins in the blood decreases, which leads to a drop in the level of total T4. In this case, free thyroxine will correspond to the norm or indicate a change in the functioning of the thyroid gland.

Reduced synthesis of thyroid hormones leads to the appearance of characteristic symptoms:

• lethargy, drowsiness;
• decrease in working capacity;
• fluid retention in the body, swelling;
• weight gain;
• mental retardation, memory impairment;
• chilliness of the limbs;
• loss of appetite;
• constipation, bloating;
• early menopause;
• infertility.

Timely referral to an endocrinologist, diagnosis and adequate therapy prevent the progression of the disease and improve the quality of life.

Treatment with a change in the content of T4 in the blood

Dysfunction of the thyroid gland, which is accompanied by an increase or decrease in the synthesis of thyroxin, leads to pathological changes in the whole organism. Timely medical assistance helps to avoid the progression of the disease and the development of complications. At the first symptoms of the disease, it is necessary to sign up for a consultation with an endocrinologist. Doctors recommend undergoing an examination of thyroid hormones at the stage of pregnancy planning, for women over 40 years old annually, as well as for patients who have previously been diagnosed with endocrine pathology - once every six months or according to the schedule prescribed by the doctor.

With hyperfunction of the thyroid gland, drugs are prescribed to suppress the synthesis of hormones (thyreostatics), an operation is performed - resection of the thyroid gland, and radioactive iodine therapy. In case of hypofunction of an organ or surgical intervention complicated by hypothyroidism, replacement treatment with thyroid hormones is recommended throughout life.

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 the pituitary gland in the brain.

The upper 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 thyroperoxidase (TPO), it is converted to 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. These free hormones T3 and T4 provide the main metabolic and biological activity. In the blood, the level of free hormones is less than 1% of the total, but these indicators are important for diagnosis.

How do T4 and T3 affect the body

Acting interrelatedly, iodinated polypeptide hormones affect the overall development of the body, activating all systems. As a result of coordinated work:

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

Deviation from the norm of any of the hormones, up or down, leads to an imbalance and can cause various deviations:

• decrease in intellectual abilities;
• violation of mental activity;
• lowering blood pressure;
• failures in contractions of the heart muscle;
• the occurrence of edema of the body;
• violations in the work of the reproductive system, up to infertility;
• the functionality of the gastrointestinal tract is impaired;
• development of coronary heart disease.

If the level of T3, T4 and TSH drops sharply during pregnancy, then this can provoke a violation of the formation of the nervous system in the fetus.

The value of analyzes

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

• TSH - regulates the production of hormones, if its level begins to rise, then 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 violation of the thyroid gland;
• the total level of thyroxine is affected by the concentration of transport proteins in the blood;
• Free T3 is involved in oxygen metabolism and its uptake by cells.

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

Norms T3, T4 and TSH for different groups of people

The norm for women is the same as for men.

Why can there be an imbalance of T4 and T3

The consequences of a lack or excess of T4 T3 hormones affect all body systems, and the causes of imbalance are deviations 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, hormonal imbalance occurs and the production of T4 and T3 can be disrupted, most often the level of 3T is lowered, especially in the first and second trimester. For the normal development of the fetus, he needs iodine, and since his own thyroid gland has not yet been formed, he draws supplies from the mother's body. To make up 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 alert 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 hormone T3 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;
• decrease in the protective functions of the body;
• the inability of tissues to recover from injury.

You can determine that the level of T3 is lowered by the following signs:

• pallor of the skin;
• reduced body temperature;
• memory impairment;
• constipation;
• poor digestion.

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

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

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

If free T3 is elevated, then this may be evidence of such diseases:

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

It is possible to determine whether the norm is exceeded in men by several signs:

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

If the hormone in women is in excess, then this can provoke:

• painful and irregular menstruation;
• frequent temperature rises;
• a sharp weight gain or, conversely, weight loss;
• mood swings, emotional outbursts;
• trembling fingers.

A child can have an elevated hormone when:

• heavy metal poisoning;
• neuropsychiatric disorders;
• due to excessive physical exertion on the body;
• development .

What affects low and high levels of T4

T4 is a hormone responsible for protein synthesis and delivering it to cells, in addition, it has a great influence on the female body - reproductive function depends on it.

If the rate of the T4 hormone 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 such diseases:

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

Most often, T4 is increased in a child with toxic goiter, when it occurs and it greatly increases in volume. In second place among the reasons is the use of drugs, 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 drugs are prescribed to a child, then they should be given strictly in accordance with the doctor's instructions.

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

In the blood, both hormones circulate in two states:

• free;
• associated transport proteins.

The total indicator is a combination of free and bound hormones.

The effect on the body of T4 of general and free is very different. The overall indicator may go beyond the norm, but at the same time, the amount of the hormone in the free state will be greatly reduced. Therefore, for an adequate analysis, information about free T4 and T3 is important. In protein-bound form, thyroxine and triiodothyronine have no effect on the body. They can circulate through the bloodstream for months and accumulate. But if the decay process is disturbed, then there will be a lack of free hormones. That is why an analysis is needed to determine free T4 and T3, as well as their general level.

It is difficult to determine which indicator is more important: T4 total or free. The most revealing analysis is during pregnancy. At this time, the amount of protein in the blood, which concentrates thyroxin in itself, greatly increases in the woman's body, so its general indicator may be normal, but the free form of the T4 hormone will not be enough, which will negatively affect the development of the fetus.

How to determine the level of hormones

To assess the functioning of the thyroid gland, or in the presence of one or more symptoms of hormone imbalance, the endocrinologist will prescribe. Before taking an analysis for the hormone T4, T3, TSH, you need to prepare:

• stop taking for a month;
• two days to exclude drugs that contain iodine;
• exclude physical activity for two days;
• try not to be nervous;
• 12 hours before you stop eating, you can only drink water
• you need to take an analysis for the hormone on an empty stomach, in the morning;

More indicative will be an analysis for free T4 in dynamics, it must be taken once a month for six months.