From Big Medical Encyclopedia

THYRITROPIC HORMONE [lat. (glandula) of thyreoidea thyroid gland + Greek tropos direction; hormone[s]; synonym: thyrotropin, Thyrotropinum, TTG] — the anterior pituitary hormone, a biological role to-rogo consists in maintenance of a normal structure and functional activity of a thyroid gland.

Of this year belongs to to proteinaceous and peptide hormones (see); it is synthesized in basphilic cells — tireotrofa (tirotrofa) of a front share of a hypophysis (see). In tireotrofa Of this year it is formed in small (the size apprx. 150 nanometers) secretory granules.

Of this year the pier is a glycoprotein with the general. it is powerful (weight) apprx. 28 000. A carbohydrate (glyconew) part of a molecule makes Of this year apprx. 15% of its weight. The molecule consists Of this year of two subunits, or alpha and beta chains. an alpha Chain of a molecule Of this year the person, just as polypeptide chains of follicle-stimulating hormone (see), luteinizing hormone (see) and a chorionic gonadotrophin (see), represents the polypeptide chain consisting of 89 amino-acid remains and differs from alpha-chains of these hormones only in a glyconew part. the beta Chain of a molecule of the person consists Of this year from 112 (according to other data, from 113) the amino-acid remains; it is various at the listed above hormones. Thus, immunol. and biol. specificity is defined Of this year by their beta chain. Believe that the a-chain protects a beta chain from effect of proteases and thus stabilizes it in the course of transportation from the place of education to a target organ.

The carbohydrates which are a part of a glyconew part of a molecule Of this year are presented faugh by a goat (see), a galactose (see), a glycosamine (see) and galaktozaminy, and also the acylated neuraminic acid (see). Carbohydrate part of a molecule does not influence Of this year it biol. activity, however assume that the carbohydrates which are contained in a molecule Of this year define time of its circulation in blood, thereby promoting biol. to effect of this hormone.

On the structure Of this year of the person it is close to Of this year cattle and differs from it only in the provision of two amino-acid remains — a lysine and a leucine and amount of sialic acids (see).

The hypophysis of the healthy person excretes per day from 30 to 200 HONEY of hormone in blood. By means of ion-exchange chromatography (see) it was established what Of this year, being in blood, differs from Of this year, formed in a hypophysis. At the person in blood Of this year circulates in the form of the intact molecule of hormone having, however, a bigger pier. weight, than usually (believe that it is pro-hormone), and also in the form of the usual (associated) molecule Of this year and separately — in a look and - subunits of hormone. After introduction of a tiroliberin — a TTG-rileasing-faktora (see. Hypothalamic neurohormones) content in blood in the form of the associated molecules increases Of this year. Tiroliberin in 2 — 4 min. after introduction stimulates release Of this year from a hypophysis. Along with it in tireotrofa synthesis amplifies Of this year, and at long stimulation tiroliberiny in a front share of a hypophysis note growth and increase in number of tireotro-f. Increase in blood of concentration of thyroid hormones of thyroxine (see) and triiodothyronine (see) synthesis and release oppresses Of this year.

Secretion finds Of this year accurately expressed day-night rhythm, for to-rogo strengthening in the blood in the period of a dream reaching 200% of the main level with a maximum of concentration of hormone at the beginning of a dream is characteristic Of this year. At experimental animals in response to stay in the environment with the lowered temperature observed sharp strengthening Of this year in blood. Long finding of animals in the conditions of low temperature led to a hypertrophy of a thyroid gland and increase in secretion of thyroid hormones.

Action on a thyroid gland is carried out Of this year with participation cyclic 3', 5' - AMF (tsAMF). Linkng with receptors of thyrocytes leads Of this year to increase in intracellular maintenance of tsAMF in 1 — 2 min. after introduction Of this year. Strengthening of tsAMF in a thyrocyte is followed by stimulation of capture of iodine gland, acceleration of iodination thyreoglobulin (see), stimulation of a resorption of a colloid and increase in emission of thyroid hormones in blood within the first 30 min. after introduction Of this year. Further in a thyroid gland note an intensification of synthesis of phospholipids, protein, RNA and DNA. Ej prostaglandin takes part Of this year in processes of synthesis, secretion and release of thyroid hormones of a thyroid gland under influence (see P growth of an aglandina). Thus, functional activity of a thyroid gland generally depends on quantity Of this year, and the speed of secretion is regulated Of this year by c. N page and a hypothalamus (see). However, e.g., at a diffusion toxic craw (see the Craw diffusion toxic) there is a formation of the peptides stimulating function of a thyroid gland, so-called tireoidstimuliruyushchy antibodies, to-rye belong to the class of immunoglobulins G. These antibodies are called it is long the operating thyroid stimulator (long acting thyreoid stimulator) — LATS, a LATS protector, a stimulator of a thyroid gland of the person, a stimulator of adenylatecyclase of a thyroid gland of the person etc. Believe that these antibodies are autoantibodies to a receptor Of this year and play the central role in a pathogeny of a diffusion toxic craw.

Concentration Of this year in blood serum of the healthy person during the definition of radio immunol. by method makes 2 — 8 HONEY/l. At newborns within the first 30 — 60 min. after the birth note high content Of this year in blood serum, a cut then during 48 — 72 hours decreases to the level characteristic of the adult.

Increase in secretion of hormone, including and at the hormonal and active adenoma of a hypophysis producing Of this year is clinically shown by a thyrotoxicosis (see). However increase in secretion is observed Of this year seldom. Note decrease in products Of this year owing to reduction of quantity of tpreotro-f, napr, at adenomas of a hypophysis and others patol much more often. the processes leading to destruction of a front share of a hypophysis. It, in turn, leads to development of a secondary hypothyroidism (see). Low secretion can be observed Of this year also at not changed function of a front share of a hypophysis, in case of disturbance of functions of hypothalamic area (see ipotalamo-pituitary system) and reduced thereof secretions of a tiroliberin (a so-called tertiary hypothyroidism).

In medicine as medicine apply the purified extract from a front share of a hypophysis of cattle — Thyrotropinum.

Thyrotropi-num represents powder of pale yellow color, easily water soluble and isotonic solution of sodium chloride (pH of solutions 5,2 — 6,0), almost insoluble in alcohol.

Drug is standardized on ability to increase the weight of a thyroid gland 3 — 5-day chickens and expressed in terms of action (PIECE). Thyrotropinum is applied for the purpose of differential diagnosis of primary and secondary hypothyroidism. With to lay down. the purpose Thyrotropinum in combination with Thyreoidinum (see) is used as medicine at insufficiency of a thyroid gland of gipotalamo-pituitary genesis.

At patients with hron. adrenal insufficiency introduction of Thyrotropinum can provoke crisis like addisonichesky crisis (see. Crises ) as a result of acute adrenal insufficiency. Besides, at use of drug nausea, skin rash, an itch and other allergic manifestations are possible. Therefore Thyrotropinum, as a rule, most often is applied with the diagnostic purpose. Drug is contraindicated at primary hypothyroidism, coronary heart disease, a sporadic and diffusion toxic craw, a hypocorticoidism.

Thyrotropinum is entered subcutaneously or intramusculary; with the diagnostic purpose enter once 10 PIECES, with to lay down. the purpose appoint 10 PIECES a day within 5 — 7 days. It is possible to repeat a course of treatment 2 — 3 times with a break in 2 — 3 months.

Produce in hermetically the corked bottles 10 PIECES, apply solvent to each bottle (an ampoule with 1 ml of isotonic solution of sodium chloride). Store in cool (at a temperature not over 10 °) the place protected from light.

See also Thyroid gland .

Bibliography: Biochemistry of hormones and hormonal regulation, under the editorship of N, A. Yudaye-va, page 10, M., 1976; The Guide to clinical endocrinology, under the editorship of B. G. Baranova, D., 1977; Starkova H. T. Clinical endocrinology, M., 1983; Hormones in blood, ed. by C. H. Gray a. V. H. T. James, v. 1, L. — N. Y., 1979; O n t j e s D. A., W a 1-t o n J. a. N e at R. L. The anterior pituitary gland, in book: Metabolic control and disease, ed. by Ph. K. Bondy a. L. E. Rosenberg, p. 1165, Philadelphia a. o., 1980; Peptide hormones, ed. by J. A. Parsons, p. 273, Baltimore a. o., 1976.

M. I. Balabolkin.