The thyroid gland (TG) consists of 2 lobes and a narrow isthmus connecting them. It looks like a butterfly, located on the front surface of the neck under the larynx, covered with cartilage. The size of the gland is 3-4 cm, and it weighs only about 20 g.
A bit of anatomy
TG determines the work of the entire endocrine system. But it's not just that it's unique. The thyroid gland is the only organ that produces hormones and stores them in reserve before they enter the bloodstream. The secretion produced is released into the circulatory system only when necessary.
The parenchyma consists of vesicles-follicles, which have only 1 layer of epithelium (thyrocytes). The unusual thing is that at rest the epithelium is flat and does not produce a secret. When the reserves are depleted, the layer takes a cubic shape and synthesizes the required amount of hormones. They are stored in the follicles in the form of thyroglobulin until they are released from the pituitary gland under the action of TSH.selection.
Inside the follicles contain a colloid. It is a viscous liquid in which thyroglobulin protein is stored. The thyroid hormone is called thyroxin, and thyroglobulin is its precursor.
Work rate
Providing the body with energy, the thyroid gland itself is controlled by another endocrine gland - the pituitary gland. He himself depends on the hypothalamus. The pituitary hormone that regulates the activity of the thyroid gland is called thyrotropin or TSH. Its function is to stimulate triiodothyronine (T3) and thyroxine (T4).
The thyroid hormones contain iodine atoms, that is, they are iodized. Deficiency of this substance always leads to disturbances in the functioning of the gland. Accordingly, iodinated hormones are called iodothyronines or thyroids. The thyroid gland produces several types of them, each of which has its own functions: T4, T3, thyroglobulin, calcitonin. The numbers indicate the number of iodine atoms.
T4 - thyroxine - biologically inactive, produced in the largest quantity - 92%. The active and main hormone is T3, which is produced from T4 by splitting off 1 atom of iodine from it. The reaction occurs when the enzyme TPO - thyroperoxidase interacts. T3 is 10 times more active than the T4 hormone.
Functions of thyroid hormones
Thyroid hormones have the following functions:
- Thyroid boosts metabolism;
- regulate the growth and development of the fetus;
- women affect reproductive function;
- with its deficiency, infertility may develop;
- take part in the synthesisvitamin A;
- regulate the work of enzymes;
- responsible for the condition of the skin and hair, the skeletal system and physical development;
- activate the brain and vascular system.
Another thyroid hormone called calcitonin will be described below.
Work and hormone formation
Free hormones make up only 1%, but they determine the entire work of the thyroid gland, the associated hormones do not function.
Some thyroid hormones are called thyroid hormones. These are derivatives of alpha-amino acids (tyrosine). The main functions of the hormone are as follows:
- he is involved in tissue growth;
- increases tissue oxygen uptake;
- promote the synthesis of red blood cells by affecting the bone marrow;
- participates in water exchange;
- affects blood pressure, stabilizing it, if necessary, increases the strength of heart contractions (with an excess of T3, heart rate immediately increases by 20%);
- accelerates thought processes and motor-psychic activity;
- responsible for metabolic processes;
- participates in thermoregulation;
- increases immunity and removes bad cholesterol;
- increases glucose levels and affects gluconeogenesis in the liver and thereby inhibits glycogen synthesis.
Participation in metabolism is expressed in the acceleration of lipolysis, maintaining harmony and normal weight. Hormones act as anabolics on protein synthesis and keep nitrogen metabolism positive (normal). When overabundant, they resemble catabolics in their action, and the nitrogen balance is disturbed.
T3 functions
Triiodothyronine free or free T3 is the name of the thyroid hormone. He is the most active of all. The two main thyroid hormones (T3 and T4) are inextricably linked, since one is formed from the other. Triiodothyronine remains the main one, although it is produced in small quantities. As mentioned earlier, the main hormone produced by the thyroid gland is called thyroxine. It is the predecessor of T3 and becomes the "engine" for the work of the whole organism:
- enhances transport of amino acids;
- allows you to digest vitamins, proteins, carbohydrates;
- helps in the synthesis of vitamin A.
What is the name of the thyroid hormone in gynecology? Often, free FT3 and FT4 are called “female”, because reproductive function in all its manifestations depends on them. When released into the bloodstream, T3 binds to transporter proteins that deliver it to the place of required presence.
T3 norm
All hormones have a dependence on the time of year, day, age and sex. The highest T3 is noted in autumn-winter, and the lowest one in summer. His level depending on age:
- from 1 to 19 years - up to 3.23 nmol/l;
- from 20 years old - up to 3, 14 nmol/l;
- from the age of 50 - up to 2.79 nmol/l.
Thyroxine
In the biological sense, it is inactive, but indispensable for humans. T4 is produced in the follicles. It is noteworthy thatthyroxine (the so-called main thyroid hormone) is produced only with the participation of thyrotropin.
FT4 and T4 are the same hormone that circulates in the blood in different ways. It should be noted that the amount of T3 always depends on T4.
T4 norm
Norm T4 St. (free) in women ranges from 71.23 to 142.25 nmol/l; in men - from 60.77 to 136.89 nmol / l. Such large intervals depend on age. The highest level of T4 was noted from 8 am to 12 noon - at this time it is best to take tests. From 11 p.m., its content drops, and the lowest level is observed at 3 a.m. Fluctuations can also be caused by various diseases. In what cases T4 St. and T3 can be increased? This happens when:
- multiple myeloma;
- obese;
- kidney disease;
- thyroid disorders after childbirth;
- thyroiditis;
- HIV;
- diffuse goiter;
- porphyria;
- liver pathology;
- after hemodialysis.
This is also possible when taking analogues of thyroxine, methadone, prostaglandins, "Cordarone", "Tamoxifen", radiopaque iodine-containing substances, "Insulin" and "Levodopa".
Decrease in hormone levels noted at:
- low protein diet;
- hypothyroidism;
- Sheehan syndrome;
- injuries;
- endemic goiter;
- inflammation in the higher levels of the endocrine system - the pituitary and hypothalamus;
- after illnesses;
- adrenal disorders.
Taking certain drugs also causes a decrease in thyroid hormones. Among them it is worth noting:
- "Tamoxifen";
- "Mercazolil";
- beta blockers;
- statins;
- steroids;
- anabolics;
- diuretics;
- "Propylthiouracil";
- muscle relaxants;
- X-ray contrast agents.
What to do when T3 rises?
First, we should not forget about the possibility of errors in research. This becomes possible if the rules for passing the analysis are not followed. Secondly, you should immediately consult an endocrinologist.
Thyrotropic hormone (TSH, TSH)
Thyrotropin is a hormone of the adenohypophysis. It plays a major role in the smooth functioning of the thyroid gland. The relationship between thyroids and TSH is inverse. The international norm for TSH is the range from 0.4 to 4.0 µIU/ml.
Thyrocalcitonin hormone
Another hormone produced by the thyroid gland is called calcitonin or thyrocalcitonin. It is produced by the parafollicular cells of the gland. It is important for calcium-phosphorus metabolism and is a parathyroid hormone antagonist.
Calcitonin reduces the level of P and Ca in the blood, and also stimulates the development and functioning of osteoblasts (bone tissue cells). This is a tumor marker that checks for the presence of thyroid cancer. If its amount exceeds 100 pg / ml, then the probability of oncological disease is high.
Also, calcitonin is an indicator of the effectiveness of cancer therapy. Analysis for this hormone is constantly taken by those whoThe thyroid gland was removed in order to diagnose a tumor recurrence in time.
Diseases that increase calcitonin levels:
- pancreatitis;
- liver cancer;
- stomach;
- liver failure;
- thyroiditis;
- pernicious anemia.
Calcitonin norm
Its rate depends on the gender of the person. With the ELISA method, calcitonin in men should be 0.68-32.26 mg / ml. For women, the norm is: 0.07-12.97 pg/ml.
Indications for thyroid hormone tests
Tests will be needed in the following cases:
- detection of signs of thyrotoxicosis (tachycardia, weight loss, tremor of the body and hands, tearfulness, nervousness, increased appetite, bulging eyes, extrasystole, etc.);
- signs of hypothyroidism (bradycardia, weight gain, slow thinking and speech, dry skin, decreased libido);
- visual and ultrasound enlargement of the gland;
- the presence of nodes in it;
- infertility;
- menstrual disorders (amenorrhea);
- fetal miscarriage;
- heart rhythm disturbances;
- lipid metabolism disorders with increased blood cholesterol;
- anemia;
- reduced sexual activity;
- galactorrhea;
- child developmental delay;
- to control treatment for gland pathologies;
- control after thyroid surgery;
- TSH analysis is included in neonatal screening, that is, it is mandatory for all newborns in Russia;
- baldness (alopecia);
- obesity.
What thyroid hormones should I take
What are thyroid hormone tests called? Everything is very simple: these are hormonal studies. The analysis is always carried out in a complex manner. That is, T3, T4 and TSH are necessarily determined.
TSH is an indicator of normal thyroid function. He is "the main one in the family", and his level in the blood is determined for any pathology of the gland. The definition of TSH is called a study of hormonal status.
T3 St. - responsible for oxygen metabolism of cells and tissues. Determination of concentration is a complex study, so mistakes are often made here.
T4 St. - responsible for protein synthesis and its stimulation. In a blood test, the doctor may also prescribe the determination of AT-TG - antibodies to thyroglobulin and AT-IPO - antibodies to tipreoid peroxidase. These tests allow the detection of autoimmune diseases and are important in differential diagnosis. Norm AT-TG from 0 to 4, 11 IU/l.
AT-TPO is the most sensitive test for detecting autoimmune processes in the gland. Represents the definition of antibodies to a cellular enzyme. The norm of AT-TPO is from 0 to 20 IU / l. Some laboratories consider 120 IU / L to be the norm, so the values \u200b\u200bof the norm should be in the forms.
Transcript of analyzes
Deciphering should be carried out only by an endocrinologist, not even a laboratory assistant.
- With an increase in TSH, one can think of hypothyroidism in a patient, but T4 and T3 are of decisive importance.
- With increased TSH andreduced T4 - obvious overt hypothyroidism. If T4 is normal against the background of elevated TSH, this is subclinical hypothyroidism.
- With normal TSH but low T4, 99% of the time the result is a lab error. A new retake of the biomaterial for analysis is required. Also a mistake will be the norm of TSH and reduced T3.
- Decrease in TSH indicates excessive activity of the organ - hyperthyroidism. At the same time, T3 and T4 (thyroid hormones) are increased. If they are within the normal range against the background of a decrease in TSH, this is subclinical hyperthyroidism.
Hormonal norm
Why can the performance of different laboratories vary? Because everywhere there are peculiarities of equipment, different models of devices for research, the difference in their settings, the reagents used.
Of course, international standards are taken as the basis for the values, but each laboratory makes its own adjustments. The difference is small, but it can lead to false diagnoses. Therefore, reference values should be indicated on laboratory forms.
Blood for thyroid hormones: what is it called
What are the thyroid hormones called, and what functions do they perform, we figured it out. Now it is important to dwell on the rules for taking tests. They are not difficult, but their knowledge and implementation will help to get true results. Some pile up a whole series of prohibitions, which, upon closer examination, are somewhat exaggerated. It is not necessary to limit yourself in nutrition. The fact is that the food taken does not affect thyroid hormones - they are so stable that the analysis can be taken atany time of the day and even right after a meal. But this is only if there is no need to donate blood for other studies.
Throughout the day, the level of TSH changes slightly. Often there are recommendations that in the treatment of hormonal drugs, their intake should be stopped a month before the study. This is an unsubstantiated assertion. Such a measure will only cause harm.
You can also find recommendations about stopping the intake of iodine-containing drugs a week before the test. However, they also do not affect performance.
Women need to remember: the level of thyroid hormones does not depend on the cycle, so you can donate blood on any convenient day. Menstruation only affects sex hormones.
But here's what's important! Before taking blood for analysis, you can not undergo X-ray, ECG, ultrasound or physiotherapy. All these examinations should be carried out 2-4 days before the procedure.
