T3 (triiodothyronine) free – the norm in women by age

Elevated T3 is the basis for the appointment of hormone replacement therapy. To reduce the concentration of triiodothyronine, take antithyroid drugs:

Medications accumulate in the thyroid gland, inhibiting the synthesis of iodine-containing hormones. After the disappearance of signs of the disease, the dose of drugs is gradually reduced. If, after refusing treatment, the T3 level rises again, resort to surgical intervention.

With diffuse goiter, radioactive iodine therapy is prescribed. It penetrates the thyroid lobes, where it begins to decay gradually. Local irradiation of the thyroid gland leads to the death of part of its cells. Due to this, its size and production of T3 decreases.

In 63% of cases, elevated T3 is due to proliferation of the gland. Therefore, with the ineffectiveness of drug treatment, a thyroidectomy is performed – removal of the thyroid gland. After surgery, patients show symptoms of hypothyroidism. To compensate for the lack of thyroid hormones, they are prescribed hormone replacement therapy.

  • Provides cellular “respiration” of tissues and organs;
  • Participates in general metabolism (metabolism);
  • Responsible for rhythm and heart rate;
  • Activates regeneration processes (cell renewal);
  • Regulates nervous excitability;
  • Stimulates the synthesis of vitamin A;
  • Reduces the concentration in the blood serum of “harmful” cholesterol.

TK is responsible for energy metabolism, i.e. helps to get energy from food and its further rational use.

Also, this hormone takes an active part in the “correct” laying of internal organs and systems in the physical development of the embryo. Therefore, the level of T3 is very important to control in planning for conception and pregnant women.

But basically, a general T3 analysis (linked by transporter proteins) allows you to diagnose abnormalities in the endocrine system and the pathology of the thyroid gland itself.

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The functions of triiodothyronine

The primary production of triiodothyronine occurs in the prenatal period, that is, even in the womb. In the absence of a hormone, the physical and mental development of the child is impossible. The synthesis of T3 is affected by other hormone-regulating organs – the hypothalamus and pituitary gland.

In the anterior pituitary gland produces thyrotropin (TSH), which stimulates the activity of the thyroid gland. It regulates the synthesis of tri- and tetraiodothyronine. In the absence of deviations in the endocrine system, the level of free T3 does not exceed 6.8 pmol / L.

An excessive content of triiodothyronine is indicated by excessive irritability, aggressiveness and fatigue. Over time, tremors of the upper limbs, heart pains occur.

In 15% of cases, elevated T3 is the result of taking hormonal and corticosteroid drugs. Hyperactivity of the thyroid gland provokes:

  • estrogens;
  • valproic acid;
  • oral contraceptives;
  • amiodarone;
  • tamoxifen;
  • methadone;
  • clofibrate;
  • terbutaline;
  • heroin etc.

Elevated triiodothyronine in a child is often caused by genetic pathologies, autoimmune malfunctions. Excessive hormone synthesis results from the production of antibodies to thyroid receptors that are sensitive to thyrotropin. The result is a diffuse growth of glandular tissue, an increase in the content of thyroid hormones – T3 and T4.

The abuse of drugs to increase potency leads to malfunctioning of the thyroid gland. According to statistics, 27% of patients who have found an increased level of T3 systematically took drugs to restore erectile function.

Many women after 45 years of age experience hormonal disorders. Often this is due to the onset of menopause. The extinction of ovarian function leads to rearrangements in the endocrine system. Increased triiodothyronine provokes excessive sweating, a sharp change in mood.

Elevated T3 free threatens with serious complications. Hormonal imbalance leads to changes in the work of several systems at once:

  • nervous;
  • cardiovascular;
  • urinary;
  • reproductive;
  • digestive
  • immune;
  • hepatobiliary.

The most negative consequences of an excess of thyroid hormones in the blood include:

  • thyrotoxic hepatosis – dystrophic changes in the liver caused by impaired lipid metabolism;
  • hypokalemic transient paralysis – a violation of the contractile activity of the muscles caused by a decrease in the concentration of potassium;
  • heart failure – a weakening of myocardial function, accompanied by congestive phenomena;
  • atrial fibrillation is a heart rhythm disorder caused by a chaotic atrial contraction.

Stably elevated levels of triiodothyronine are dangerous thyrotoxic crisis. It manifests itself as shortness of breath, hypertension, diarrhea, tachycardia, abdominal pain, mental over-excitation. For 35-50% of patients, a thyrotoxic crisis results in death.

Hyperthyroidism in pregnant women negatively affects the development of the fetus. Antibodies to thyrotropin receptors are transmitted to the child by a transplacental route. Because of this, newborns are diagnosed with transient hyperthyroidism.

Indicators of normal serum T3 may have differences. It depends on the methods that are used in the conditions of this laboratory.

When using immunochemiluminescent analysis, which is particularly accurate, normal values ​​are in the range from 2,62 to 5,69 pmol / L. When using methods with reduced sensitivity, the upper limit of the normal state rises to 5,77 pmol / L.

However, these values ​​are averaged. For men, women and children of different ages, they can change.

In childhood, the amount of hormone in a free state is higher than the average norm. There are differences depending on gender.

Indicators of normal serum T3 may have differences. For men, women and children of different ages, they can change.

In a young child, the normal range is 2,9-7,5 pmol / L for boys and 3,5-8,3 pmol / L for girls. At the age of five, the norm increases significantly: in boys up to 2,5–9,2, and in girls up to 4,6–9,8. In the age range from 7 to 10 years, the normal amount of free triiodothyronine increases to a value of 4-22,9 in boys and 4-17,2 in girls.

In adolescence, free triiodothyronine gradually decreases its performance, reaching by the age of 16 years 3,7-7,7 in boys and 3,8-6,0 in girls.

Such a change in the norm is associated with the growth of the body and hormonal changes. To ensure these processes, a lot of energy is needed, which is formed during the activation of oxidative processes using triiodothyronine.

After 18 years, the growth of the body stops, and the hormonal background is stabilized. The body’s need for energy is reduced, which forces the body to produce matter in smaller quantities.

Thyroid: the formation of thyroid hormones. Part 1

The thyroid gland: the effect of thyroid hormones on the body – Part 2

Triiodothyronine belongs to thyroid hormones, although it is synthesized in the thyroid gland in very small amounts – about a fifth or fourth. The main share is formed in the kidneys and liver when iodine is cleaved from thyroxine (T4). The hormonal activity of triiodothyronine (T3) is high, but in order for it to appear, it must be free of bonds with proteins.

It is free hormone molecules that interact with the nuclei of cells, accelerate metabolism, bone growth, enhance heart function, change vascular tone, and affect brain activity. A blood test for free triiodothyronine is important for determining the function of the thyroid gland, monitoring changes in its activity during treatment, and the need for dose adjustment of drugs.

In the body, the hormone is responsible for such functions:

  • Regulation of oxygen supply to tissues.
  • The formation of proteins from amino acids.
  • Increasing blood sugar by stimulating the formation of new glucose molecules in the liver and breaking down glycogen stores.
  • The breakdown of fats, cholesterol.
  • Strengthening the secretion of bile to cleanse the body of fatty acids.
  • Contraction of the intestinal wall (intestinal motility).
  • The construction of bone tissue.
  • Synthesis of male and female sex hormones, vitamin A and absorption of vitamin B12 from the intestines.
  • The formation of the nervous system in childhood.
  • Increased functional activity of the cerebral cortex.
  • Increased sensitivity of cells to insulin and growth hormone growth hormone.
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Thyroid hormone synthesis

Analyzes for thyroid hormones are performed if there is a suspicion of serious malfunctions in the endocrine system, with an increase or decrease in the gland, with nodes and tumors.

A thyroid test is performed using laboratory blood tests. List of indicators for the study:

  • thyroid-stimulating hormone (TSH);
  • triiodothyronine (T3);
  • thyroxine (T4);
  • antibodies to thyroglobulin (AT-TG);
  • antibodies to thyroid peroxidase (AT-TPO).

When evaluating the results, it must be remembered that hormone standards may vary, because they depend on the technological features of the testers in the laboratories. You should also pay attention to the “reference values” – this is a quantitative range, which is the norm for a particular type of analysis.

What the indicator says:

  • a normal amount of thyroid-stimulating hormone indicates the stable functioning of the pituitary gland;
  • increased TSH is a sign of a lack of thyroid hormones, which indicates primary hypothyroidism;
  • A TSH below normal indicates hyperactivity of the gland; in this situation, hyperteriosis is diagnosed.

TSH during pregnancy fall below normal in the first trimester. If a woman before pregnancy did not have pathologies in the thyroid gland, the process of lowering thyroid stimulating hormone in the first trimester (especially with multiple pregnancy) is the norm that does not require treatment.

Features T3 and T4

The thyroid gland produces tetraiodothyronine and a small amount of triiodothyronine – only 20% of the total body needs. The necessary 80% of T3 is produced in other organs (in the liver, kidneys, central nervous system) as a result of the decay of T4. It is characteristic that in women, the processes of T4 to T3 conversion occur worse than in men.

Thyroid hormones are in the body in two forms: in free and bound form. It is the free forms of thyroxine and triiodothyronine that are used for metabolic processes. Hormones in bound form are the result of the attachment of protein molecules. The total is the amount in total, that is, free and associated hormones.

The level of free T3 in the blood is insignificant compared with total triiodothyronine (approximately 0,03%).

Lack of general and free T3 is a symptom of the following diseases:

  • hypothyroidism;
  • kidney failure;
  • liver failure.

An increase in total and free T3 occurs in diseases of the thyroid gland, kidneys, liver and endocrine system as a whole:

  • thyrotoxicosis;
  • isolated toxicosis T3;
  • toxic goiter;
  • thyroid dysfunction after childbirth in women;
  • chronic and acute nephritis;
  • chronic liver disease;
  • obesity;
  • drastic weight loss;

A decrease in indicators indicates:

  • hypothyroidism;
  • atrophic thyroiditis;
  • nephrotic syndrome;
  • gastrointestinal diseases, in which there is a significant loss of protein.

Excessive production of total and free tetraiodothyronine is observed during pregnancy, during the treatment with the artificial drug thyroxin, as well as in obesity.

An increase in T4 indicates the development of the following diseases:

  • hyperthyroidism;
  • toxic thyroiditis;
  • hepatitis.

During pregnancy, the norm of total and free T4 for women increases, since the normal development of the fetus depends on the level of tetraiodothyronine. In women during pregnancy, an increase in T4 is accompanied by symptoms of a rapid heartbeat, frequent attacks of hunger and a headache. In the second and third trimester, free thyroxine is reduced to normal.

AT-TPO. Thyroid peroxidase (TPO) is an enzyme that is produced by the thyroid gland, through which hormones are formed. Antibodies to TPO are proteins that bind and neutralize the necessary enzyme, thereby impairing the functioning of the gland.


Data on the level of triiodothyronine are used to conduct differential (comparative) diagnostics of thyroid diseases, as well as to control the hyperthyroid state (excessive production of endocrine hormones).

In addition, a general T3 test is an essential part of screening (a comprehensive examination for hormones) of the thyroid gland in the following cases:

    thyro >

With toxic toxic diffuse goiter, as well as thyroid adenoma, formations may appear that additionally produce triiodothyronine, which leads to T3 toxicosis. In this case, the hormone level is analyzed to evaluate the effectiveness of the treatment.

Total T3 increased

A high concentration of the hormone in the blood indicates various forms of thyrotoxicosis, which is accompanied by a rather vivid clinical picture:

  • increased nervousness, aggression, frustration, emotional instability;
  • sleep disorders (insomnia, frequent awakenings);
  • fatigue, loss of strength;
  • trembling of fingers, hands (tremor);
  • arrhythmia (heart rhythm disturbance), extrasystole (additional myocardial contractions);
  • rapid pulse (tachycardia);
  • sharp and unreasonable weight loss;
  • frequent urge to urinate;
  • indigestion (diarrhea);
  • fever (rarely);
  • menstrual cycle disorders;
  • breast enlargement in male patients.

An increase in the concentration of T3 total against the background of normal indicators of other thyroid hormones is considered a false positive result.

True excess of the norm indicates the following pathologies:

  • Graves’ disease (an autoimmune disease that leads to poisoning by thyroid hormones);
  • isolated T-thyrotoxicosis or TSH-independent thyrotoxicosis;
  • hyperthyroidism;
  • thyroiditis (inflammation of the thyroid gland of an autoimmune nature);
  • malfunctioning of the thyroid gland after childbirth;
  • thyroid adenoma;
  • nephrotic syndrome (kidney damage, accompanied by increased swelling of the tissues);
  • thyroid hormone resistance;
  • Pendred’s syndrome (genetically determined enlargement of the thyroid gland).

Classification of triiodothyronine in endocrinology

  • Bound, which moves through the bloodstream not independently, but entering into a relationship with proteins;
  • Free – for transportation to the desired site the substance does not require a “partner”, because the hormone remains in the bloodstream in an unchanged state, which enhances its biological functions. It is in its free form that the T3 hormone is present in greater quantities in the human bloodstream of both women and men.

In a laboratory blood test for triiodothyronine, the parameters of total T3, free and bound, are studied to get a complete clinical picture.

Women who have normal T3 counts are always energetic, have increased working capacity, and emotional balance. If even a slight hormonal imbalance occurs, symptoms of depression, irritability, decreased concentration, loss of working capacity, mood swings and lack of motivation are observed. Rapid weight loss or weight gain is often the result of an imbalance in the production of thyroid hormones.

Changes in the mood, appearance, or character of a woman can be an occasion to contact an endocrinologist, who must prescribe a blood test for thyroid hormones.

Total T3 below normal

As a rule, a reduced level of total T3 is observed in case of a violation of the secretory function of the thyroid gland, when a decrease in the concentration of other endocrine hormones is recorded. In this case, patients note symptoms:

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  • fatigue, lethargy, drowsiness, weakness of muscles and ligaments (low energy potential);
  • causeless numbness of arms and legs;
  • convulsive syndrome;
  • digestive disorders (nausea and vomiting, constipation, lack of appetite);
  • increased swelling of tissues (including facial area);
  • violation of potency;
  • low body temperature (loss of strength).

A similar clinic can be observed in the following conditions:

  • Hashimoto’s thyroiditis is an autoimmune process, accompanied by the death of thyroid cells and a violation or complete loss of its secretory function;
  • toxic goiter (nodular, diffuse, etc.) – when treating a disease with special drugs, a high chance of developing hypothyroidism. Also, the concentration of T3 decreases during treatment with radioactive iodine;
  • surgical intervention on the thyroid gland (its full or partial removal);
  • thyroid insufficiency, which first leads to a decrease in the concentration of the hormone T4, and then T3;
  • thyroiditis (subacute and acute form);
  • decreased secretion of thyroxin-binding globulin;
  • renal dysfunction, renal failure;
  • cirrhosis of the liver ;
  • anorexia (nervous form);
  • malnutrition (starvation, low protein diet);
  • acute iodine deficiency in the body;
  • preeclampsia and eclampsia (a form of late toxicosis with critically high blood pressure and seizures);
  • rehabilitation period after severe illness.

Based on the history and available symptoms, the doctor writes out a referral for analysis of total triiodothyronine. Interprets the results of an endocrinologist or diagnostician.

Norm of hormone T3 free in women: table, analysis (preparation), deviations (symptoms, causes, treatment)

The thyroid hormones thyroxine (T4) and triiodothyronine (T3) are involved in many important body support processes. As a result of the removal of one iodine molecule from thyroxin, triiodothyronine is formed.

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There are free and bound forms of hormones. The norm of the hormone T3 is free in women – a marker of the functioning of her thyroid gland.

Deviations both up and down from the norm may indicate the development of pathologies in the body.

The thyroid hormones thyroxine (T4) and triiodothyronine (T3) are involved in many important body support processes.

Age of patientReference values ​​T3 free, pmol / l
Up to a year1,4 – 4,8
1-3 years3,5 – 8,3
3-5 years4,6 – 9,8
6-7 years4,0 – 11,0
Younger school age2,0 – 8,0
Girls 14-18 years old3,2 – 6,0
Women 20-50 years old3,6 – 6,8
Women older than 50 years2,6 – 5,6

Regardless of the age of a pregnant woman, the level of triiodothyronine of an unbound form has lower values, which is not a pathology. During pregnancy, the T3 free indicator is in the range of 2,1-5,1 pmol / L.


A referral to an analysis to determine the unrelated form of the T3 hormone is given by an endocrinologist or therapist. Sometimes such a diagnostic measure is carried out on the recommendation of a gynecologist.

To conduct studies to determine the concentrations of free triiodothyronine, venous blood is used.

The study of biomaterial is carried out by radioimmunological or immunochemiluminescent methods. An enzyme immunoassay is also applicable.


To obtain accurate analysis results, a number of requirements must be observed:

  • blood is given exclusively on an empty stomach (preferably in the morning);
  • 2-3 weeks before the delivery of the biomaterial, you should refuse to take hormonal and other drugs;
  • a day before the diagnosis, it is recommended to stop drinking alcohol and smoking;
  • the day before the examination should abandon the use of spicy, fatty foods and energy drinks;
  • on the eve of the study, it is advisable to avoid heavy physical and emotional stress.

If refusal to take medications is not possible, it is necessary to inform the attending physician and laboratory assistant about this.

Only a specialist can correctly decipher the results of a blood test. Based on the obtained laboratory data, the symptoms of the disease and the collected medical history, as well as taking into account the results of other studies, the doctor prescribes the appropriate therapy.


Deviation of the content of T3 free in blood serum from the norm can be both upward and downward. This analysis result indicates the development of some dangerous diseases in women.


With insufficient production of triiodothyronine in a woman, the following are diagnosed:

  • fatigue, lethargy, weakness;
  • frequent colds due to reduced immunity;
  • nausea, vomiting;
  • swelling of the limbs and face;
  • metabolic disease;
  • low blood pressure.

A reduced level of T3 free in a woman’s body can manifest itself as frequent convulsions, constipation, dizziness.

Symptoms of excess unbound T3 are:

  • frequent headaches;
  • high blood pressure;
  • a sharp set or deficit of body weight;
  • tremor of extremities;
  • digestive upset.

With a high content of T3 in the blood of a woman, the menstrual cycle may be violated, problems with conceiving and carrying a pregnancy can occur.


Among the causes of deviations in women, the level of triiodothyronine to a greater extent is distinguished:

  • thyrotoxicosis;
  • toxic goiter;
  • hyperthyroidism;
  • genetic diseases;
  • lack of iodine in the body;
  • liver disease;
  • pathology of the kidneys.

Sometimes an excess of the hormone is diagnosed in women in the postpartum period. The growth of unbound T3 in the blood can be caused by pituitary adenoma and tumor neoplasms.

Low T3 free in women is observed with:

  • the development of Hashimoto’s syndrome;
  • thyroiditis progression;
  • the development of familial dysalbuminemic hyperthyroxinemia;
  • renal and hepatic failure;
  • hypofunction of the thyroid gland.

The hormone deficiency is diagnosed with anorexia, the use of iodine in the treatment of diffuse goiter. A reduced level of unbound T3 or its absence is often observed with partial or complete removal of the thyroid gland.


Therapy of excess free triiodothyronine is complex. The doctor prescribes sedatives, vitamin complexes and drugs that reduce the production of iodine-containing hormone.

Along with taking medications, a woman is obliged to follow a special diet and daily regimen. During the treatment period, it is desirable to protect the patient from excessive emotional and physical stress.

To reduce the concentration of T3 unbound, caused by increased activity of thyroid cells, they resort to radioiodine therapy.

With a low level of free hormone T3, the doctor prescribes the intake of hormonal drugs. In severe cases, for example, with intensive development of goiter, specialists resort to surgical intervention. In this case, part or all of the organ is removed.

Scientific studies of thyroid hormones have shown that triiodothyronine (T3) is several times more active than its predecessor hormone thyroxine (T4), which is provided by nature for the full functioning of the whole body. If there is a violation of the level of free triiodothyronine in the female body, the following symptoms begin to manifest:

  1. Frequent mood swings without any reason.
  2. Systematic headaches that are difficult to relieve with analgesics.
  3. Anger for no reason, which has a short or long manifestation.
  4. Violation of thermoregulation, accompanied by a constant increase or decrease in body temperature, which is recorded during daily measurement with a thermometer. A woman may have complaints of constant chills or sweating, even without changes in ambient temperature.
  5. Stool disorders (diarrhea or constipation).
  6. A sharp decrease in body weight or weight gain without cause for a short time period. An endocrinologist suggests a metabolic disorder due to an increase or decrease in free triiodothyronine in a woman relative to normal indicators.
  7. Minor physical activity, walking accompanied by shortness of breath.
  8. Failure in the menstrual cycle. In some cases, a woman completely stops the blood (state of amenorrhea).
  9. Trembling limbs even in a calm state. The endocrinologist observes the tremor in the patient when she asks her to extend her arms in front of her, and they begin to tremble.
  10. Strengthening the work of sweat glands, when a woman has excessive sweating, even in a cool room without physical exertion.

There may be delays in brain activity, impaired memory, when a woman cannot formulate her thoughts or remember new information. The concentration of attention is also disturbed, a breakdown is observed. Even simple work leads to overwork.

If the listed symptoms are in the woman’s complaints, it can be assumed that the free T3 level is not normal and the patient needs a comprehensive examination and treatment.

Even if there are vivid symptoms of a deficiency or excess of T3, a blood test must be taken for the entire group of hormones, including thyroid stimulating hormone (TSH), thyroxine (T4) and triiodothyronine in general and free form. Only having the digital values ​​of all hormones on hand, the endocrinologist can make an accurate diagnosis or prescribe a woman a more in-depth study.

Only a laboratory study of a woman’s venous blood provides accurate information about the hormones of all the endocrine glands, including the thyroid and pituitary glands, which produce TSH, T4 and T3.

When referring a woman to the study of hormones, the endocrinologist gives instruction on the rules of the procedure and the necessary preparation of the patient for the event:

  • The analysis is given in the morning only on an empty stomach;
  • A few days before the biomaterial is taken, the taking of medicines and products that can affect the level of substances of interest in the woman’s body is excluded;
  • Avoid overvoltage, stressful situations before analysis.

If a woman complies with the recommendations for the rules of analysis, then the results will be correct and the endocrinologist will compare them with the criteria for the T3 norm of free, taking into account the age and individual characteristics of the patient.

What is considered the norm can be found in the table above, but the doctor can use other indicators to make a diagnosis.

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An increase in T3 in the body inevitably leads to changes in the functioning of internal organs. The following symptoms indicate endocrine disorders:

  • muscle weakness;
  • fatigue;
  • increased appetite;
  • thinning hair;
  • tachycardia or bradycardia;
  • temperature increase;
  • trembling of hands;
  • loose stools;
  • protrusion of eyeballs;
  • sleep disturbance;
  • sharp weight loss;
  • high blood pressure;
  • emotional lability;
  • violation of the menstrual cycle;
  • feeling of palpitations in the stomach.

With increased T3 in the elderly, myocardial dystrophy occurs – a violation of the myocardial function caused by its depletion. The disease is fraught with cardiosclerosis, ascites.

Catabolic syndrome is one of the first signs of an increase in the level of triiodothyronine. It is characterized by a sharp decrease in weight, excessive sweating and increased appetite. People with thyrotoxicosis do not feel cold, even with a strong decrease in ambient temperature.

With an increased content of thyroid hormones, disorders occur on the part of the eyes – the rise of the upper eyelid, buccal eye, chronic conjunctivitis against the background of incomplete closure of the eyelids. The face of the patient acquires an expression of anger or fear. Symptoms indicate diffuse toxic goiter.

With a moderate increase in the concentration of T3, the ability to conceive is rarely reduced. But the progression of the disease during pregnancy is fraught with neonatal thyrotoxicosis in newborns. It is manifested by fetal tachycardia in the last trimester of gestation, hypertension and poor weight gain after birth.

Preparation for analysis

  • Blood sampling for analysis on T3 total is performed exclusively in the morning (until 11.00) and strictly on an empty stomach.
  • The day before the procedure, fatty, smoked, spicy and salty, tonic and alcoholic drinks should be excluded from the diet.
  • Also, during the day you need to abandon any physical activity: sports, sex, weight lifting, jogging, dancing, etc. In addition, it is advisable to protect yourself from psychological stress and nervous shocks. And 20 minutes before the manipulation, you should completely relax and calm down.
  • A few hours before the analysis, you must refrain from smoking, chewing tobacco or using nicotine substitutes.

Important! It is necessary to inform the attending physician in advance of all recent or current courses of drug treatment. In women who take oral contraceptives, the analysis is carried out only after they are canceled.

Before donating blood, the endocrinologist in 15-20 days cancels drugs that increase or decrease thyroid function. If there are vital preparations for the patient, then their list is indicated in the referral form. Typically, the subject comes to the laboratory after a 10-12-hour night break in food intake. As an exception, you can allow a 4-hour day interval.

For a day, it is important to completely abandon alcohol, physical and emotional stress, and for an hour – from smoking. If the analysis is reassigned to study the reaction to the use of medicines, it is advisable to take it in the same laboratory and at the same time of the day as the previous one.

What is the difference between free and general

The total amount of triiodothyronine includes the following compounds:

  • Free form of the hormone (less than 1%).
  • T3 associated with thyroxin-binding albumin.
  • T3 with prealbumin.
  • Triiodothyronine in combination with globulin.

The relationship between the hormone and transport proteins in T3 is lower than in T4, so it undergoes cleavage and elimination from the body faster. Its concentration in the blood is low.

The test for the free part of T3 recently entered the practice of endocrinologists, therefore there is not enough experience in interpreting (explaining the changes) of its level in various diseases. Most often, this analysis is assigned in dynamics to assess the results of treatment, and TK common is used as an indicator of the severity of damage to the thyroid gland.

Indicators in the analysis in women, children and men

Blood is taken from a vein and serum is isolated from it by centrifugation. After the addition of antibodies labeled with the enzyme, complexes with triiodothyronine are formed. Then, a chemiluminescent substrate is placed in the tube and a glow appears, recorded by the device. The result of the analysis is issued the next day.

Also, when evaluating the results, the following features are taken into account:

  • After 65 years, a physiological decline is noted.
  • During pregnancy, the norm is considered to be a gradual decrease in the concentration of T3 free and recovery a week after birth.
  • Low indicators are associated with low-calorie nutrition, lack of protein, rapid weight loss, severe physical exertion, hot climate or summer period of the year.

A high level of free hormone means an increase in thyroid function. The reasons for this may be:

  • Acute, subacute or chronic inflammation (thyroiditis).
  • Bazedov’s disease (diffuse goiter with thyrotoxicosis).
  • Short-term iodine deficiency in food.
  • Hyperthyroidism (isolated) amid increased T3.
  • A tumor (often benign) in the thyroid gland, pituitary gland.
  • Violation of tissue sensitivity to thyroid hormones.
  • Deficiency of the thyroid-stimulating hormone of the pituitary gland (total T3 normal).

I can lead to an increase in T3 of free tumors: myeloma (blood cancer) and chorionocarcinoma (neoplasm of the fibers of the embryonic tissue), kidney and liver diseases. Medications that can increase the hormone content are birth control pills, hormones with estrogen or levothyroxine, and drugs.


Low thyroid function is a congenital pathology, and also appear against a background of infection or autoimmune disorders, it provokes:

  • Long-term iodine deficiency.
  • Diseases of the pituitary or hypothalamus.
  • Exhausting diseases of the internal organs.
  • Mental disorders.
  • Extensive operations.
  • The use of Cordarone, anabolics, beta-blockers, Finlepsin, Dexamethasone, testosterone.

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Diagnosis of thyroid disease: methods .

Complete diagnosis of thyroid diseases includes several methods – ultrasound, laboratory, differential, morphological, cytological, radiation. There are features of the examination in women and children.

Perhaps you want to know about the new medication - Cardiol, which perfectly normalizes blood pressure. Cardiol capsules are an excellent tool for the prevention of many heart diseases, because they contain unique components. This drug is superior in its therapeutic properties to such drugs: Cardiline, Recardio, Detonic. If you want to know detailed information about Cardiol, go to the manufacturer’s website.There you will find answers to questions related to the use of this drug, customer reviews and doctors. You can also find out the Cardiol capsules in your country and the delivery conditions. Some people manage to get a 50% discount on the purchase of this drug (how to do this and buy pills for the treatment of hypertension for 39 euros is written on the official website of the manufacturer.)Cardiol capsules for heart
Tatyana Jakowenko

Editor-in-chief of the Detonic online magazine, cardiologist Yakovenko-Plahotnaya Tatyana. Author of more than 950 scientific articles, including in foreign medical journals. He has been working as a cardiologist in a clinical hospital for over 12 years. He owns modern methods of diagnosis and treatment of cardiovascular diseases and implements them in his professional activities. For example, it uses methods of resuscitation of the heart, decoding of ECG, functional tests, cyclic ergometry and knows echocardiography very well.

For 10 years, she has been an active participant in numerous medical symposia and workshops for doctors - families, therapists and cardiologists. He has many publications on a healthy lifestyle, diagnosis and treatment of heart and vascular diseases.

He regularly monitors new publications of European and American cardiology journals, writes scientific articles, prepares reports at scientific conferences and participates in European cardiology congresses.