Thyroid hormones are biologically active substances that are synthesized in the thyroid gland (thyroid gland), are iodinated derivatives of tyrosine and are involved in many metabolic processes in the body, according to Pannochka, an online publication for girls and women from 14 to 35 years old.. net Thyroid hormones are among the main regulators of metabolism.. Thyroxine (T4) contains 4 iodine atoms, triiodothyronine (T3) - 3 atoms.
Depending on the chemical structure, all hormones are divided into types:.
steroid;
amino acid derivatives;
derivatives of polyunsaturated fatty acids;
protein-peptide.
Thyroid hormones are derivatives of the amino acid tyrosine.. Synthesis and activation of the main thyroid hormone - thyroxine - occurs with the participation of thyroid-stimulating hormone (TSH) - a glycoprotein of the anterior pituitary gland. Thyroxine is formed as a result of the addition of iodine (iodination) to the proteinogenic amino acid L-tyrosine.
Of the total amount of synthesized thyroid hormones, 60-80% enters the bloodstream in the form of thyroxine, a significant part of which is then converted into triiodothyronine, which has a greater activity.. Thyroxine itself weakly binds in tissues to thyroid hormone receptors..
The conversion of thyroxine to triiodothyronine occurs with the help of selenium-dependent monodeiodinase.. In the presence of a congenital defect of monodeiodinase (its reduced activity in tissues), a lack of selenium in the body and / or the use of a number of drugs, a person may experience a deficiency of thyroid hormones against the background of a normal level of thyroxine in the blood.
Functions of thyroid hormones in the human body The functions of T3 and T4 are:.
Metabolism activation.
Stimulation of processes that ensure the growth and development of the body, differentiation of tissues.
Stimulation of gluconeogenesis in the liver.
Increasing the concentration of glucose in the blood and its utilization by body cells.
Decreased glycogen production.
Inhibition of fat deposition and enhancement of its breakdown (lipolysis).
Increased heart rate, blood pressure, body temperature.
Stimulation of motor and mental activity.
Increasing the body's demand for oxygen.
ten. Increase tissue sensitivity to catecholamines.
eleven: Increased erythropoiesis in the bone marrow.
In addition, the properties of T3 and T4 include participation in water metabolism.
Depending on the level of T3 and T4 in the blood, they have different effects on protein metabolism.. So, low concentrations of these substances have an anabolic effect (they can increase the formation of proteins and inhibit their breakdown), and high concentrations have a catabolic effect (inhibition of protein production and increased their breakdown).
Signs of abnormality In case of insufficient production of these biologically active substances, the patient may experience:.
pallor of the skin (possible yellowish tinge);
lethargy and fatigue even with minimal physical exertion;
increased hair loss;
deterioration in memory and concentration;
depressive states;
arterial hypertension;
weight gain;
tachycardia;
decreased sex drive;
liver enlargement.
If the thyroid gland secretes more thyroid hormones, you may experience:.
tremor;
drastic weight loss;
disorders of the gastrointestinal tract;
mental disorders;
heart disorders.
With a decrease in the ability of the thyroid gland to absorb iodine and iodine tyrosine, the patient may develop a goiter, which compresses nearby anatomical structures, makes it difficult to breathe, swallow.
Diseases of the thyroid gland affect the synthesis of thyroid hormones by it Laboratory determination of the concentration of T3 and T4 Most of the T3 and T4 is in the bloodstream in a bound form. Albumin and thyroxin-binding globulin are able to bind thyroxine and triiodothyronine.. In addition, T4 is able to bind to transthyretin.. Only a small part of thyroxine and triiodothyronine circulates in the blood in a free form and is their biologically active fraction..
For this reason, the determination of free triiodothyronine and thyroxine is of particular importance.. In addition, the concentration of free T4 does not depend on the content of thyroxin-binding globulin, which allows the use of this diagnostic parameter in physiological and pathological conditions that are accompanied by a change in the concentration of this protein (pregnancy, congenital disorders).
Indications for the appointment of an analysis for suspected thyroid disease;
to control the effectiveness of the treatment;
during a preventive medical examination;
during childbearing (impaired production of T3 and T4 can lead to abortion, the occurrence of pathologies in the development of the fetus);
children of the first days of life born to mothers with thyroid pathologies.
The table shows the normal values \u200b\u200bof the free fraction of thyroxine and triiodothyronine in the blood.
Index.
Reference values.
Free triiodothyronine (free. T3).
2.3–4.2 pg/ml.
Free thyroxine (free. T4).
0.89-1.76 ng / dl - for men and non-pregnant women 0.86-1.87 ng / dl - I trimester of pregnancy 0.64-1.92 - II-III trimesters of pregnancy.
Rules for passing the analysis1. Blood to determine the level of T3 and T4 should be taken in the morning (preferably before 11:00).
8-12 hours after the last meal.
Before the study, it is necessary to exclude mental and physical overload, the use of fatty foods.
What to do if there is a violation of the production of thyroxine and triiodothyronine If the concentration of T3 and T4 in the blood deviates from the norm, the treatment regimen depends on the cause of the pathological process, the patient's symptoms, contraindications.
Patients need to give up bad habits, avoid stressful situations, normalize the daily routine and adhere to the diet prescribed by the doctor..
If the thyroid gland does not produce enough thyroid hormones, hormone replacement therapy is indicated for the patient.. With excessive synthesis of these substances, antithyroid drugs are used.. In some cases, surgery is required.
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