Download presentation of the thyroid gland in Kazakh. The thyroid gland (glandula thyroidea) is an endocrine gland that synthesizes a number of hormones necessary to maintain homeostasis. Thyroid. Thyroid ultrasound

HYPOTHALAMO-ADENOGYPOPHISAL-THYREOID OSTIREOLIBERIN
HYPOTHALAMUS
thyrotropin
adenohypophysis
THYROID
TARGET ORGANS
T3 and T4

STAGES OF THYROID HORMONE SYNTHESIS AND SECRETION

THYROID HORMONES

PHYSIOLOGICAL EFFECTS OF IODINE-CONTAINING HORMONES

METABOLIC EFFECTS OF THYROID HORMONES

MAIN FUNCTIONS OF CALCIUM

MAIN FUNCTIONS OF CALCIUM

MAIN FUNCTIONS OF CALCIUM

MAIN FUNCTIONS OF CALCIUM

THREE CALCIUM REGULATORY HORMONES

Parathyroid glands (according to Guyton, 2006)

The main effects of parathyroid hormone

Other effects of parathyrin

MAIN EFFECTS OF CALCITONIN

Effects of Calcitonin

Effects of Calcitonin

Effects of Calcitonin

SUMMARY

MAIN MILESTONES IN THE HISTORY OF CALCITRIOL STUDIES

FORMATION OF CALCITRIOL

REGULATION OF CALCITRIOL FORMATION

Mechanism of action of calcitriol

MAIN EFFECTS OF CALCITRIOL

EFFECTS OF CALCITRIOL

EFFECTS OF CALCITRIOL

Description of the presentation on individual slides:

1 slide

Description of the slide:

Thyroxine Functions: Thyroxine affects all tissues of the body, there are no specific target cells for it. This hormone is able to cross the membrane and bind to receptors in every cell of the body. The main function of thyroxin is the activation of metabolic processes, which is carried out through stimulation of the synthesis of RNA and corresponding proteins. Thyroxin affects metabolism, increases body temperature, controls the growth and development of the body, increases protein synthesis and sensitivity to catecholamines, increases heart rate, thickens the internal mucosa lining of the uterus in women. It enhances oxidative processes in the cells of the whole organism, in particular, in brain cells. Thyroxine is important for the proper development and differentiation of all cells in the human body, and can also stimulate vitamin metabolism.

2 slide

Description of the slide:

Triiodothyronine Function: Synthesized as a metabolite of tyrosine. Under the action of a special peroxidase, I- ions in the thyroid gland are attached to tyrosine residues in the high molecular weight protein thyroglobulin. From 1/5 to 1/3 of the total amount of thyroid hormones produced by the thyroid gland enters the blood immediately in the form of triiodothyronine. The remaining 2/3-4/5 enter the blood in the form of biologically inactive thyroxine, which is actually a prohormone. But in peripheral tissues, thyroxine, with the help of the metalloenzyme selenium-dependent monodeiodinase, undergoes deiodination and is converted into triiodothyronine.

3 slide

Description of the slide:

Calcitonin (thyreocalcitonin) Functions: Thyrocalcitonin is involved in the regulation of phosphorus-calcium metabolism in the body, as well as the balance of osteoclast and osteoblast activity, a functional antagonist of parathyroid hormone. Thyrocalcitonin lowers the content of calcium and phosphate (parathyroid hormone antagonist) in the blood plasma by increasing the uptake of calcium and phosphate by osteoblasts. It also stimulates the reproduction and functional activity of osteoblasts. At the same time, thyrocalcitonin inhibits the reproduction and functional activity of osteoclasts and the processes of bone resorption.

4 slide

Date: 10/11/16

The thyroid gland and its hormonal functions. Diseases in violation of the function of the thyroid gland. Measures for the prevention of thyroid diseases in the Republic of Kazakhstan.

The thyroid gland (glandula thyroidea

The thyroid gland (glandula thyroidea) is an endocrine gland that synthesizes a number of hormones necessary to maintain homeostasis.

PATHOLOGY

Clinical manifestations of thyroid diseases are due either to excessive or insufficient production of thyroid hormones, or excessive production of calcitonin and prostaglandins (for example, in medullary carcinoma - a calcitonin-producing tumor), as well as symptoms of compression of the tissues and organs of the neck of an enlarged thyroid gland without impaired hormone production (euthyroidism).

Five degrees of enlargement of the thyroid gland:

About degree- the gland is not visible during examination and is not determined by palpation;

I degree- when swallowing, the isthmus is visible, which is determined by palpation, or one of the lobes of the thyroid gland and the isthmus are palpated;

II degree- both lobes are palpable, but on examination, the contours of the neck are not changed;

III degree- the thyroid gland is enlarged due to both lobes and the isthmus, visible when viewed as a thickening on the anterior surface of the neck (thick neck);

IV degree- large goiter, not sharply asymmetric, with signs of compression of nearby tissues and organs of the neck;

V degree- extremely large goiter.

CAUSE OF THYROID DISEASES

• stress
• increased level of solar activity
• hereditary predisposition
• iodine deficiency

• premature or late puberty,
• violations menstrual cycle,
• anovulation,
• infertility,
• not carrying a pregnancy,
• pathology of the fetus and newborn.

Thyroid function disorders in the form of hypo- and hyperthyroidism are observed with its various pathologies:

• Graves' disease;
• nodular toxic goiter;
• multinodular toxic goiter;
• subacute thyroiditis;
• asymptomatic thyroiditis;
• iodine-induced thyrotoxicosis.

Thyrotoxicosis (hyperthyroidism)

increased levels of thyroid hormones.

Most often, thyrotoxicosis syndrome develops with diffuse toxic goiter (disease

Graves-Basedow),

multinodular toxic goiter,

subacute thyroiditis,

with an overdose of thyroid hormone preparations, etc.

Clinical manifestations of thyrotoxicosis syndrome include damage to various organs and systems .

Heart rhythm disturbances (tachycardia, extrasystole, paroxysmal atrial fibrillation)

Arterial hypertension

Increased excitability, tearfulness

sleep disorder

Tremor of outstretched fingers, tremor of the whole body

Unsteady stool, abdominal pain

Weight loss

Subfebrile body temperature (temperature rise up to 37-38°C)

Hot skin, sweating

increased appetite

muscle weakness

Impaired glucose tolerance

Exophthalmos (protrusion of the eyeball)

diffuse alopecia

Diffuse toxic goiter (Graves-Basedow disease)

Graves' disease is a systemic autoimmune disease characterized by a persistent pathological increase in the production of thyroid hormones, usually in combination with a diffuse enlargement of the thyroid gland and extrathyroid disorders (endocrine ophthalmopathy).

Endocrine ophthalmopathy - manifested by the expansion of the palpebral fissure, patients rarely blink,

pretibial myxedema manifested by hyperemia of the skin of the anterior surface of the lower leg, in this area are formed edema and tissue compaction.

In most cases, this symptomatology is accompanied by itching in the anterior surface of the lower leg.

Characteristic for acropathies is a thickening of the phalanges of the fingers due to swelling of the dense tissues of the phalanges and periosteal bone formations.

On x-ray examination, periosteal formations of bone tissue (phalanges of the fingers, bones of the wrist) resemble bubbles of soap suds

Hypothyroidism

Hypothyroidism Syndrome- decreased hormone production

Most common causes hypothyroidism- chronic autoimmune thyroiditis. due to thyroid surgery

irradiation,

lack of iodine

taking certain medications.

Clinical picture

Puffiness of the face

Swollen tongue, with imprints of teeth along the edges

Alopecia (hair loss on the head), thinning of the eyebrows, eyelashes

chilliness

Pastosity of the legs

Fat metabolism disorders (increased levels of triglycerides, LDL)

Menstrual irregularity

There are primary, secondary and tertiary hypothyroidism.

If the decrease in thyroid function occurs due to a lack or absence of the stimulating effect of thyroid-stimulating hormone (TSH) or releasing hormone (TSH-RG), then we are talking about secondary and tertiary hypothyroidism pituitary or hypothalamic genesis, respectively (at present, these forms are often combined into one - secondary hypothyroidism).

In the primary form the process leading to the development of hypothyroidism is localized directly in the thyroid gland (a congenital defect in the development of the thyroid gland, a decrease in the volume of its functioning tissue after surgery / inflammation, destruction radioactive iodine or a tumor, etc.).

nodular goiter

Nodules in the thyroid gland occur as a result of iodine deficiency. They are distinguished by their autonomy, since the hormones of the pituitary and hypothalamus do not act on them. Often such autonomous nodes synthesize hormones with increased activity, then symptoms similar to Graves' disease develop. If the nodule is very small, appoint conservative treatment. In severe cases, carry out surgical intervention or treatment with radioactive iodine.

Diagnostics

• General blood analysis
• Blood chemistry
• Hormonal blood test (TSH, T4 free, T3 free, etc.)
• Immunological blood test (AT to TPO, AT to TG, AT to TSH receptors, etc.)
• ECG, Cardiovisor, Cardiocode, 24-hour ECG and blood pressure monitoring
• Thyroid ultrasound
• Elastography thyroid gland - a new method of soft tissue imaging based on differences

characteristics of elasticity, allows you to more clearly differentiate malignant tumors and

other educations.

• Thyroid scintigraphy can show - the whole organ has an increased function
• or in the gland there is a node with increased function (one or more hyperfunctioning nodes).

TSH: structure, role in the body, functions

Thyrotropic hormone (TSH, thyrotropin, TSH) is a glycoprotein produced by the anterior pituitary gland that affects the ability of the thyroid gland (TG) to form iodine-containing hormones. The thyrotropin molecule consists of two subunits: alpha (a) and beta (b). Biological effects are due only to the b-subunit.

TSH is produced in the adenohypophysis after thyroliberin (TRH) stimulation of the hypothalamus. Possessing affinity for the A-cell receptors of the thyroid gland, thyrotropin activates the mechanisms for the production and release of thyroid hormones (TG): thyroxine (T4) and triiodothyronine (T3). Reaching the optimal concentration in the blood, these substances, according to the principle of negative feedback reduce the work of the hypothalamic-pituitary endocrine system.

In the event of a breakdown in any link "hypothalamus - pituitary gland - thyroid gland - target organs", changes occur in all systems of the human body without exception, since thyroid hormones regulate metabolic processes in tissues.

Causes that affect the production of TSH:

The action of thyrotropin is mainly aimed at maintaining the functional health of the thyroid gland, the systemic effect of this hormone is not expressed:

Despite the fact that the effect of TSH on the body as a whole is limited, if there is a deviation from the norm, severe symptoms can be observed. These effects are due to the resulting diseases of the thyroid gland. The physiological effects of thyroid hormones are presented in the table:

TSH study

The main indications for determining the level of TSH:

• diagnosis of thyroid diseases (presence of signs of hypo- or hyperfunction, enlargement of the gland, etc.);
• assessment of the effectiveness of thyroid hormone replacement therapy (with hypothyroidism, after removal of the thyroid gland, etc.);
• screening of newborns in the maternity hospital for hypothyroidism, pregnant women in the first trimester.

For a correct assessment of the pathology, thyrotropin is recommended to be studied together with T3 and T4, their free fractions (only free TGs carry out their biological effect, and protein-bound fractions constitute a reserve).

Pathological processes of the thyroid gland lead to the occurrence of autoimmune reactions, when the body produces antibodies to its own tissues and receptors. In this case, a study of various autoantibodies is prescribed:

• antibodies to thyroglobulin (AT-TG);
• antibodies to thyroid peroxidase (AT-TPO);
• antibodies to the thyroid-stimulating hormone receptor (AT-RTTG): stimulating and blocking.

If a change in the very structure of TSH or its receptor is suspected (for example, in congenital or familial forms of hypothyroidism due to mutations in the genes that determine their structure), a genetics consultation is prescribed.

In many cases, it is useful to examine the level of iodine, since it is an indispensable element for the synthesis of iodothyronines.

Calcitonin is another thyroid hormone produced by C-cells. His study is prescribed for suspected tumor formations. CEA (cancer embryonic antigen) is also a tumor marker.

Training

Basic rules for preparing for the study:

• The material of study is venous blood. It is taken on an empty stomach (at least 8 hours after eating).
• The optimal time for analysis is before 10 am (this is due to the daily rhythm of TSH production).
• 1-2 days before the laboratory test, it is recommended to refrain from drinking alcohol and fatty foods. Do not smoke one hour before blood sampling.
• It is advisable to indicate all medications that are taken at the time of blood donation.
• Before the study, it is necessary to limit the adverse factors affecting the result: physical stress, emotional arousal. It is necessary to observe a sleep schedule before a blood test, since the production of thyroid-stimulating hormone is maximum at night during sleep and decreases if a person is awake at this time.
• Blood should not be donated after an ultrasound, X-ray, or physiotherapy.
• The study is desirable to take place in the same laboratory, since the methods of conducting, reagents and standards for deciphering the results may differ.

Normal TSH levels

The norm of TSH, thyroid hormones and antibodies is shown in the table:

Children show the following:

The level of TSH in men is stable, while in women it varies depending on age and reproductive function.

In pregnant women normal performance TSH is slightly reduced. The differences in numbers are due to the fact that the placenta produces chorionic gonadotropin, which has an a-subunit structure similar to thyrotropin and cross-reacts with thyroid receptors. An increase in the formation of hormones by the feedback principle lowers TSH level. Also, in pregnant women, the value of thyroxin-binding globulin doubles, and iodine uptake increases.

Age TSH norms women have the following:

Result interpretation

A rise or fall in TSH levels can occur due to the following pathologies:

Level change in women of reproductive age

Most often, the TSH level is affected by the state of the thyroid gland. Thyroid-stimulating hormone is extremely sensitive to the slightest change in the level of T3 and T4. It repeatedly increases or decreases, even if thyroid hormones have not yet crossed the normal range. This makes it possible to identify subclinical forms of thyroid diseases that do not yet have pronounced symptoms.

Allocate the following types functional disorders:

• Manifest hypothyroidism - increased TSH, decreased T4.
• Subclinical hypothyroidism - an increase in TSH, T4 within the normal range.
• Manifest hyperthyroidism, thyrotoxicosis - decrease in TSH, increase in T4 and / or T3.
• Subclinical hyperthyroidism - a decrease in TSH at the rate of T4 and T3.

In hypothyroidism, only the level of T4 can be taken into account. If hyperthyroidism is suspected, both hormones must be determined, since T4 may be normal, and T3 may be elevated. Manifest forms are accompanied by the following symptoms in a patient:

An increase in autoantibodies is detected in the following diseases:

• Autoimmune Hashimoto's thyroiditis - AT-TPO.
• Graves' disease - Ab-TPO, stimulating Ab-RTTG.
• Cancer of the thyroid gland - AT-TG.

Sometimes, with severe hypertrophy of the thyroid gland, the levels of thyroid-stimulating hormone, T3 and T4 do not go beyond the normal range. This condition is called euthyroid goiter. It may be associated with iodine deficiency. The mass of the gland compensatory increases in order to capture more iodine and produce enough hormones. The norm of iodine consumption is 100-200 mcg per day.

Deviations from the norm in children

In children, secretory imbalance can be congenital or acquired. Congenital insufficiency of thyroid hormones has a huge negative impact on the child.

In newborns in the maternity hospital, a study for hypothyroidism is mandatory. For this, blood is taken from the heel, applied to a special filter paper and TSH is examined in a dry spot of whole blood. Normally, at the 13th week of intrauterine development, the thyroid gland is already functionally complete and provides the child with a sufficient amount of hormones. If the level is lowered, this has great consequences for the child's body. There are types of hypothyroidism:

• Primary - associated with the pathology of the thyroid gland.
• Secondary - occurs with an anomaly in the function of the pituitary gland.
• Tertiary - defeat of the highest level of endocrine regulation - the hypothalamus.

With the resistance of target organs to the action of hormones, the indicators may be normal or increased, but they do not show the desired effect. This is due to mutations in the genes responsible for the structure of hormones or their receptors. Rarely, hypothyroidism in a child is due to maternal blocking antibodies that cross the placental barrier and lead to decreased thyroid function.

Changes in hormone levels depending on the type of hypothyroidism:

With a lack of thyroid hormones in children, the nervous system first of all suffers, growth and body proportions decrease, sexual development- all these are signs of cretinism.

Changes in indicators in pregnant women and women in menopause

In pregnant women, it is very important to monitor the TSH values ​​​​in the first trimester, when the fetal thyroid gland is inactive, and the level of T3 and T4 depends on the maternal. For this reason, a woman's hypothyroidism is more dangerous for the child's central nervous system than the insufficiency of his own gland (the laying of the nervous system occurs in the first weeks of development, in the absence of the influence of thyroid hormones, the pathology is irreversible).

Hyperthyroidism during pregnancy is diagnosed much less frequently, with timely therapy with thyreostatic drugs, undesirable effects on the fetus can be avoided. In women during the gestation period, iodine deficiency often occurs. His daily rate for pregnant women is 200 mcg. With a deficiency, goiter may develop in both the mother and the fetus.

Women over 35 years of age should regularly check the amount of thyrotropin. After menopause (more than 50 years), the risk of developing hypothyroidism increases several times. The manifestation of hyperthyroidism at this age is extremely rare.

Conclusion

A specialist should interpret changes in the level of TSH, taking into account individual characteristics that can affect this indicator.

In most cases, thyrotropin only reflects the reaction of the higher level of the endocrine system to a non-optimal amount of thyroid hormones.

Synthesis and secretion of thyroid hormones

The endocrine system is an important and complex mechanism regulation of vital processes in the body. It is safe to say that it is no less important than the human brain. endocrine glands produce hormones that have great importance for the functionality of all human tissues. Thus, the thyroid gland affects all metabolic processes. It is thyroid hormones that help children develop properly - both physically and mentally, and for adults they give energy, and are also the main link in metabolic processes. Synthesis of thyroid hormones is controlled nervous system, to be more precise, this mechanism is controlled by releasing factors located in the hypothalamus, as well as substances that the pituitary gland produces. Thyroid hormones are always at the same level, and their concentration increases only when the body needs it. In case of their decrease, one can suspect an iodine deficiency in the body or the fact that the performance of the thyroid gland has decreased, which may indicate the development of pathology.

Structure of thyroid hormones

The basis for the thyroid hormone is the thyreonine nucleus, which has two molecules of L-tyrosine in its composition. According to their chemical formula, thyroid hormones belong to derivatives of amino acids, in particular thyreonine. It has been proven that all thyroid steroids differ in the number of iodine molecules - there are 3 or 4 of them, respectively, triiodothyronine - T3 and tetraiodothyronine - T4 are distinguished.

Types of thyroid hormones

Free T3 is a fundamental thyroid hormone. In its free form, it is responsible for the saturation of cells with oxygen and energy. In addition, it performs the following work in the body:

• regulates cholesterol and triglycerides in the blood plasma;
• promotes the excretion of calcium;
• accelerates the metabolic metabolism of carbohydrates and proteins;
• takes part in the synthesis of vitamin A in liver tissues;
• regenerates and restores bone tissue;
• has a positive effect on brain tissue and heart muscle;
• has a direct effect on the formation and growth of the embryo.

T4 free is required for:

• cellular metabolism - protein, heat, vitamin, energy, and so on;
• regulation of processes that occur throughout the central nervous system;
• stimulation of the production of vitamin A;
• suppression of triglyceride and cholesterol activity;
• metabolic changes in bone tissue.

Synthesis of thyroid hormones

The synthesis and secretion of TSH and thyroid hormones is a series of complex chemical reactions, which can be explained as follows. Thyroid hormones are substances in the structure of which there is pure iodine (more precisely, its molecules). In this regard, their synthesis requires constant capture of iodine, the following occurs in the A-cells of the thyroid gland:

• a cavity is formed inside the cells, which consists of thyroglobulin;
• thyroglobulin is the basis for the synthesis of thyroxine and triiodothyronine;
• when pituitary thyroid-stimulating hormone enters the follicular cavity, the process of production of thyroid hormone begins inside the cell;
• iodine molecules are involved in this process;
• thyroid amino acid is also required for production;
• In order for thyroid hormones to be transported to the tissues of the body, thyroid-binding globulin, TSH, is needed.

In order to understand in more detail the features of the synthesis of thyroid hormones, you can go to humbio, where this process is considered in more detail.

Functions of thyroid hormones

Thyroid hormones affect all cells human body- they affect protein synthesis, metabolism, regulate the development of bone length, improve the body's susceptibility to catecholamines (for example, adrenaline), and are responsible for the formation and function of neurons. In addition, thyroid hormones control the metabolism of proteins, fats and carbohydrates - this happens due to the impact on energy connections. Vitamin metabolism and heat metabolism are under their control.

So, the thyroid hormone receptor genes perform the following functions:

• increase cardiac output;
• increase heart rate;
• speed up metabolism;
• increase sympathetic activity;
• regulate growth;
• responsible for brain development
• saturate the endometrium in women.

Hyperthyroidism

If the norm of thyroid hormones deviates upward, a hormonal failure occurs, resulting in disturbances in the work of the whole organism as a whole.

The reasons why the thyroid gland begins to produce increased amount hormones, a lot, provoking factors are the following:

• heredity;
• genetic changes in the functionality of the thyroid gland;
• influence of unfavorable factors;
• prolonged stress;
• age changes.

Hyperthyroidism is accompanied by the following pathological conditions:

• sleep disturbance, severe excitability;
• disruptions in heart rate and breathing;
• sudden weight loss despite a normal appetite;
• visual impairment;
• diarrhea;
• sweating;
• temperature rise.

Such processes are quite dangerous for a person, since in this case the body is depleted, as resources begin to be spent very quickly. When diagnosing hyperthyroidism, specialists are repelled precisely from deviations from the norm of TSH (it decreases), T3 and T4 (they increase).

Hypothyroidism

If the norm of thyroid hormones deviates in opposite side(their level decreases) hypothyroidism develops. The main reason for this phenomenon is the lack of iodine in the body. Most often, older women suffer from this pathology.

This pathology can lead to the following ailments:

• osteoporosis;
• problems in the liver;
• infertility;
• strokes;
• heart attacks;
• decreased libido.

It is possible to suspect such a deviation from the norm by the following signs:

• constipation;
• drowsiness;
• lack of appetite and weight gain;
• decrease in heart rate;
• decrease in body temperature.

Such patients will have to take hormone replacement drugs, and possibly for life.

Thyroid hormone standards

Indicators of thyroid hormones depend on the amount of thyroglobulin, iodine and on the proper functioning of the whole organism as a whole.

The norm of thyroid hormones is as follows:

• T3 free - from 1.2 to 4.2 units;
• T4 free - from 10 to 25 units;
• T4 general - from 60 to 120 units.

In order to more accurately anticipate the level of thyroid hormones, such indicators as the concentration of thyroid-stimulating hormone and thyroglobulin, the presence of antibodies, TSH, and the ratio of thyroid-stimulating hormone to T4 are taken into account.

It is important to understand that the rate of thyroid hormones may vary depending on the age and gender of the patient.

Analysis for thyroid hormones

An analysis for thyroid hormones is prescribed in the following cases:

• differential diagnosis of pathologies in the thyroid gland;
• control of hormones in established pathologies;
• evaluation of the effectiveness of hormone replacement therapy;
• pregnancy;
• monitoring babies who were born to women with pathologies of the endocrine system;
• identifying the causes of infertility;
• developmental disorders in adolescence;
• weight change that is not associated with nutritional errors;
• cardiac pathologies;
• preventive examination of residents of regions in which endocrine diseases are often diagnosed.

In order for the determination of the hormonal status to be accurate, it is necessary to prepare for the delivery of thyroid hormones:

• a month to stop taking drugs that can affect the functioning of the thyroid gland;
• three days to exclude the intake of iodine-containing drugs;
• a day to exclude spicy and fatty foods, alcohol, energy;
• for a day to maintain a state of rest - do not play sports, do not lift weights, do not be nervous;
• the last meal before the tests should be 10-12 hours before;
• two hours before the analysis, you must stop smoking and use nicotine substitutes;
• half an hour you need to calm down, avoid fast walking.

It is not recommended to decipher the analysis of thyroid hormones on your own; this should be done by a qualified specialist.

Thyroid hormones: synthesis, functions, norm, excess and deficiency

• What are the main hormones secreted by the thyroid gland?
• How is thyroid hormone levels regulated?
• Thyroid hormones: their role and functions
• Functions of thyroid hormones
• Too much or too much thyroid hormone
• Deficiency or lack of thyroid hormones
• Functions of calcitonin

What are the main hormones secreted by the thyroid gland?

Thyroid hormones have many effects on the human body. But not everyone knows which hormones are thyroid hormones.

Hormones are biologically active substances that act on other cells of the body remotely. Thyroid hormones also affect all cells in the human body. The thyroid gland produces three active hormones:

• triiodothyronine
• thyroxine (tetraiodothyronine)
• calcitonin

When talking about thyroid hormones and diseases associated with them, most often they mean triiodothyronine and thyroxine (tetraiodothyronine). Conventionally, they are designated T3 and T4. They got their name due to the presence of iodine molecules in their composition. Triiodothyronine has three iodine molecules, and thyroxine has four.

Calcitonin is involved in calcium metabolism and development skeletal system. It is produced by the C cells of the thyroid gland.

You will probably object that these are not all thyroid hormones, since, as a rule, TSH (thyroid-stimulating hormone) also surrenders. In fact, TSH is not a thyroid hormone, it is a hormone of the pituitary gland - an endocrine organ that is located in the cranial cavity and has a regulatory effect not only on the thyroid gland, but also on other endocrine organs.

T3 and T4 in the blood are in a free and protein-bound state. Basically (more than 99%), the bound fraction of the hormone circulates in the blood, and only 0.2–0.5% falls on the free fraction. The biological effect is free fractions of hormones. These hormones have different strengths.

The most active is T3, so there is not so much of it in the blood and it is he who has all the biological effects. But T4 is no less important. It is he who turns into T3 as needed.

How is thyroid hormone levels regulated?

In endocrinology, the regulation of hormones (not only the thyroid gland) occurs according to the principle of negative feedback. The fact is that almost all endocrine organs control the central glands - the pituitary gland and the hypothalamus.

They produce their own hormones that affect the functioning of the so-called peripheral endocrine glands. The pituitary gland synthesizes thyrotropin, and the hypothalamus synthesizes thyrotropin-releasing hormone. The hypothalamus is the highest regulatory organ, followed by the pituitary gland.

For each endocrine organ, the pituitary gland produces one hormone, it can both reduce and increase its function. But how does he know when to stimulate and when to block the work of the gland? Nature arranged everything in such a way that this system regulates itself. Let's take the example of the thyroid gland.

Thyrotropin (TSH) is the regulating hormone of the pituitary gland for the thyroid gland, you can follow the link and read about it. When for various reasons the level of T3 and T4 decreases, for example, with iodine deficiency, the stimulus goes to the higher organ, after which the pituitary gland begins to increase the synthesis of TSH so that it stimulates the thyroid gland even more, and it, in turn, produces as many hormones as needed .

Conversely, when the thyroid gland produces more of its hormones, which happens, for example, with diffuse toxic goiter, a signal is sent to the pituitary gland that there are a lot of hormones and TSH is not needed yet, so the hormone level decreases or its secretion is completely suppressed.

Thus, we can conclude that with an increased work of the thyroid gland, thyroid hormones are increased, and TSH is reduced. When the thyroid gland is reduced and thyroid hormones are reduced, but thyroid-stimulating hormone rises.

The synthesis and secretion of thyroid hormones is dependent on the time of day, i.e., it has a circadian rhythm. The highest concentration of hormones in the morning. There is also a dependence on the time of year. For example, in winter, the production of triiodothyronine (T3) increases, while the level of T4 does not change significantly.

This is probably what caused the increased need for a synthetic hormone in people receiving replacement therapy in winter. After taking L-thyroxine, it turns into the active hormone T3, the need for which is just increased in winter.

It will also be useful for you to know how Euthyrox affects the development of pregnancy. Read the article "Eutiroks and pregnancy: compatibility, doses, side effects."

Be prepared in advance so that the situation does not take you by surprise.

Thyroid hormones: their role and functions

Since the thyroid gland produces two types of hormones (iodine-containing and calcitonin), we will talk about each separately.

Functions of thyroid hormones

Thyroxine and triiodothyronine have an effect on the entire body. They support normal level main exchange. Basal metabolism is the amount of energy that is spent on maintaining life in a state of complete rest, i.e., energy for the work of the heart, intestinal motility, maintaining constant temperature bodies, etc.

Thyroid hormones are responsible for:

1. protein synthesis in any cell of the body
2. cell respiration, i.e. oxygen uptake by cells
3. stimulation of bone and brain growth
4. maintaining a constant body temperature
5. involved in the process of gluconeogenesis
6. regulation of fat and carbohydrate metabolism
7. involved in cholesterol metabolism
8. erythrocyte maturation
9. ensuring reabsorption in the intestine
10. activation of the sympathetic nervous system
11. influence on water exchange
12. influence on cognitive functions of the brain
13. arterial pressure
14. participation in reproductive function

When there is an increase in thyroid hormones, the basal metabolic rate is accelerated, and when a decrease occurs, it slows down. Below you will see the effect of different amounts of hormones on the organs, i.e. manifestations.

Too much or too much thyroid hormone

• Increased heart rate
• The pressure rises
• Body temperature rises
• Increased sweating
• Diarrhea occurs
• Decreased body weight
• There is trembling in the body and restlessness

Deficiency or lack of thyroid hormones

• Pulse rare
• Pressure is often low
• Decreased body temperature
• Constipation occurs
• Skin is dry and rough
• Increase in body weight
• There is slowness and lethargy

In fact, you have learned about the most common symptoms of thyrotoxicosis and hypothyroidism. Therefore, if you notice these symptoms in yourself or in your loved ones, we recommend that you go to an appointment with an endocrinologist. There are diseases when hormones are normal, for example, with benign adenoma of the thyroid gland.

Functions of calcitonin

The role of this peptide hormone is still being studied. This hormone does not affect metabolism, but is involved in the regulation of calcium metabolism and the functioning of the cells of the skeletal system. If T3 and T4 are determined in order to assess the functioning of the thyroid gland, then calcitonin is needed for other purposes.

As a rule, this indicator is a tumor marker for medullary thyroid cancer. Together with parathyroid hormone, calcitonin is involved in the life of bone cells. They have the opposite effect of each other. Calcitonin performs the following functions:

• increases the activity of osteoblasts - cells that create new bone tissue
• reduces the concentration of calcium in the blood

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Macroanatomy of the thyroid gland