In the human body, there are two main mechanisms of regulation of organs and systems: nervous and humoral. The first of them is carried out thanks to the abundant innervation of all internal organs, glands, blood vessels and the musculo-ligamentous apparatus.
The second mechanism acts due to the distant action of hormones, in which they are produced in the endocrine gland, and then are transferred to the target tissue or organ with a blood stream. So, the hormone testosterone, the main androgen, is produced in small quantities in the adrenal cortex, and when puberty occurs in boys it begins to be actively produced in the testes, then it is secreted through the excretory ducts from the glands into the blood and then affects the musculoskeletal system, and also on metabolism in the liver. Based on the feedback principle, testosterone is able to regulate the production of other sex hormones (both in the female and in the male body).
Testosterone function
The level of testosterone in men, of course, is much higher than its level in women, because in the male body it performs more functions: in the puberty period in boys, under its influence, the formation of the so-called secondary sexual characteristics, namely: “breaking” of the voice, expansion of the shoulder girdle in comparison with the pelvis, increase in muscle mass and tightening of bones, maturation of gametes in the gonads.
In adult men, it also helps maintain sexual function, that is, sexual desire, potency, and forms psychophysiological sexual behavior. The hormone testosterone is also produced in women: in the adrenal cortex, ovaries, and by converting estrogen. It has an inhibitory effect on the maturation of follicles in the ovaries and regulates the production of estradiol and estrone through the hypothalamic-pituitary-adrenal system. With its hypersecretion in women or artificial administration of preparations containing this hormone (many anabolic steroids), women develop masculinization, which manifests itself in coarsening of the voice, increased hair growth, muscle development and aggressive behavior.
Regulation of testosterone secretion
There are several mechanisms that affect testosterone levels. Its norm in men is 11-33 nmol / liter, and in women - only 0.24-2.7. At the same time, the hormone testosterone is in the blood in two fractions: free and associated with transport proteins albumin and specific globulin, capable of binding sex hormones (SHBG). However, only free (2% of the total) and albumin-associated testosterone exhibits biological activity. After 30-35 years in men, the hormone testosterone, both its bioavailable and total fractions, tends to decrease with an average rate of 2-3% / year, and in old age the level of active testosterone is reduced by 5 times (compared with youth) , and the total - 2.5 times. According to some reports, this is explained not only by a gradual decrease in its secretion, but also by increased binding to SHBG, as a result of which the bioavailable fraction is deactivated.