Thyroid hormones. Thyroid. Endocrinology
The thyroid gland is the most important organ of the human body. Any diseases of this gland can be a cause of disorders in the work of many other human organs or systems. To prevent many serious diseases, it is very important to diagnose any pathologies and changes in the functioning of the thyroid gland in a timely manner and as soon as possible. The main method of diagnosis in this case will be a hormonal blood test. This is the most modern and accurate diagnostic method that is able to determine the slightest fluctuations in the quantitative level of hormones during blood tests and to determine abnormalities in work or the early stages of diseases of this organ.
The human thyroid gland consists of two types of cells. These are follicular cells that constantly produce the hormones T3 (triiodothyronine) and T4 (tetraiodothyronine) and parafollicular cells that produce another type of hormone - calcitonin.Triiodothyronine and tetraiodothyronine are obtained in the synthesis process from the amino acid tyrosine with the active participation of iodine compounds, which is a link. The iodothyronines formed in this way are transported and transported by proteins by the blood flow. In a pair of T3 and T4, triiodothyronine has the main biological effect, and tetraiodothyronine in this case serves as a prohormone, which is already converted into triiodothyronine (T3) in body tissues.
Thus, thyroid hormones can be defined as iodine derivatives of the amino acids tyrosine produced by the thyroid gland, which have similar physiological properties.
The process of regulation of the human thyroid gland
The main regulators of the functioning of the thyroid gland are the hypothalamus and pituitary. The brain hypothalamus, or the so-called coordination center, controls the entire work of the nervous and endocrine systems of the human body. The functions of the pituitary gland are to secrete a certain amount of hormones that are complex in their structure. The synchronous and coordinated work of the hypothalamus and the pituitary gland in this case is very important, since they are elements and links of one chain and interact as elements with feedback.
Thus, if the total hormone level in the gland falls, then specific receptors determine this and deliver information to the hypothalamus. The hypothalamus begins to produce liberins, the task of which is to have an impact on the pituitary gland. He begins to release TSH or thyroid-stimulating hormone, forcing the thyroid gland to intensively produce T3 and T4. In the reverse situation, when the hormones in the bloodstream become more necessary, the hypothalamus transmits the substance of statins to the pituitary gland. This process of self-regulation allows you to maintain a constant and optimal level of hormones in the blood for all tissues and organs.
The process of synthesizing thyroid hormones
The synthesis of thyroid hormones is the main function of the thyroid gland. That it plays a decisive role in the metabolism of iodine for the human body. Iodine is extracted by the thyroid gland from the blood, accumulates in it and is used in the synthesis of hormones.
Phase hormone synthesis
The very process of the synthesis of these hormones can be divided into five main phases.
- Synthesis of thyroglobulins.
- Accumulation of iodides in the thyroid cell.
- Oxidation of iodides and their transformation into organic iodine compounds.
- As a result, receive iodothyronines, which are thyroid hormones.
- The entry of blood hormones T3 and T4, secreted from thyroglobulin as a result of the process of proteolysis.
The main functions of the hormones T3 and T4 in the human body
Triiodothyronine and tetraiodothyronine are directly related and actively influence the work of the human body as a whole. It is on them that the reduction or enhancement of heat generation, the heat productivity of the body, and the activity of the capture of oxygen by all organs depend on it. Thyroid hormones of the thyroid gland maintain at the optimum level the respiratory functions, acting directly on the center of respiration, stimulate the functionality of the myocardium, the motility of the intestinal region, initiate the formation of red blood cells.
In addition, the normal level of these hormones affects the formation and growth of proteins throughout the body. Therefore, without thyroid hormones, there is no growth and proper development of absolutely all human tissues and organs.
Thyroid hormones: normal
The total number of T3 and T4 depends mainly on the balanced work of the endocrine system as a whole, on the quantitative composition of iodine and thyroglobulin.
Laboratory standards for the quantitative level of thyroid hormones are as follows:
- free T3 should normally be from 1.2 to 4.2 pMM / l;
- total T4 normally should be from 60 to 120 nmol / l;
- free T4 should normally be from 10 to 25 pMM / L.
For more accurate laboratory determination of the level of hormones of this type in the blood, such indicators as levels of thyroglobulin and thyrotropic hormone are used; the presence of antibodies to thyroglobulin; TSH; the ratio of T4 to thyroid stimulating hormone.
Consequences of abnormal thyroid hormones
With a clear lack of hormones in the blood and, accordingly, in human tissues and organs, when the optimal balance of functioning of the systems and organs is disturbed, a disease such as hypothyroidism develops. Hypothyroidism is characterized by such signs as lethargy, baldness, pale or yellow face tinge, sclerosis, decreased intellectual ability, frequent bouts of depression, weight gain, hypertension, tachycardia, an increase in liver size, and extinction of sexual function.
Another disease associated with increased levels of the hormones T3 and T4 is thyrotoxicosis.It develops in the case of the active release of hormones from the gland into the blood when this process becomes uncontrollable, and the level of hormones in the bloodstream rises sharply (so-called hyperthyroidism). Thyrotoxicosis is clinically manifested by such symptoms as thyroid goiter, pep-eyed, mental abnormalities, tremors, sudden weight loss, angina and changes in myocardium, liver dystrophy, diarrhea, changes in the reproductive system, in both men and women.