Physiological functions of androgens and common sense about human health

I. Androgens (Testosterone)

(I) Production and Metabolism

Under the influence of pituitary gonadotropins, the testes synthesize androgens and produce sperm. Androgens are steroid hormones containing more than a dozen carbon atoms. There are several types of steroids with androgenic activity, mainly testosterone, androstenedione, dehydroepiandrosterone (DHEA), and estrone, with testosterone exhibiting the highest activity.

In men, approximately 95% of plasma testosterone is secreted by the interstitial cells of the testes, with the remainder originating from the zona reticularis of the adrenal cortex. In women, the adrenal cortex is the primary site of androgen production; ovarian hilar cells also secrete small amounts of androgens. The zona reticularis primarily produces DHEA, so the difference in this hormone between the sexes is minimal. A normal male secretes approximately 8 mg of testosterone daily, with a plasma concentration of about 0.6 μg/100 ml, while the plasma testosterone concentration in women is only 0.3 μg/100 ml.

Testosterone is secreted directly from the interstitial cells of the testes into the intertubular tissue. It is released from the testes via three routes: venous blood flow in the seminal vesicles, lymph, and reticulum testis. Most testosterone in plasma is bound to plasma testosterone-binding globulin; very little exists freely (0.2%–3%). Testosterone is primarily degraded in the liver. Except for a small amount (5%) that is completely oxidized, most is reduced and then recombined (with glucuronic acid) to become physiologically inactive substances, which are then excreted from the body through the kidneys.

(II) Physiological Functions

Androgens play an important role in promoting spermatogenesis, maintaining the development of male accessory sex organs, and promoting and maintaining secondary sexual characteristics and sexual function. In addition, testosterone also promotes metabolism: it increases the activity of RNA polymerase and aminoacyltransferases on ribosomes, thus promoting protein synthesis; it promotes increased bone matrix synthesis, which is beneficial for calcium salt deposition, thus promoting bone growth; and it increases the production of erythropoietin in the kidneys, stimulating erythrocyte production. Androgens reduce the amount of fat stored in the body during fat metabolism.