The role of Testosterone in male reproductive system (review)

Testosterone is a hormone that is predominantly formed in Leydig cells adjacent to the seminal tubules of the testis, in the ovaries and adrenal cortex [1, 5, 6]. Testosterone production is regulated by the hypothalamic-pituitary system under the guidance of gonadotropin-releasing hormone (GnRH) and luteinizing hormone (LH), between which there is negative feedback [5-6]. In addition to GnRH and LH, testosterone is also interconnected with other hormones: melatonin [14], oxytocin [15], thyroid hormones [16]. Testosterone has a great effect on the body of animals. Thus, it promotes the growth and maturation of bone tissue [17], prevents oxidative damage to the brain [19-20], affects metabolism [21], as well as animal behavior [23]. In addition, studies have noted the important role of the hormone in spermatogenesis. Testosterone, binding to the androgen receptor, regulates the proliferation and maturation of Sertoli cells, maintains the integrity of the blood-brain barrier, regulates the meiotic and post-meiotic processes of germ cells [27-30]. The effect of the hormone on sperm cryoresistance is noted, however, some authors emphasize the negative effect of testosterone on cryoresistance [32- 33], while others point to a beneficial effect [34]. In females, testosterone, together with other androgens, binds to androgen receptors, changes the activity of other receptors, and also interacts with growth factors [36]. Studies show that the hormone, together with LH, is able to stimulate the production of progesterone [37]. It is known that many factors influence the dynamics of testosterone in the blood. For example, with the passage of age, androgens in the blood decrease in bulls [41], however, in adult rams, the testosterone content is 1.8 times higher than in younger individuals [43]. Another factor worth noting is animal feeding: studies show that a diet with a higher protein content contributes to a positive effect on animals, as well as increases hormone levels [44-45]. In addition, heat stress suppresses the expression of enzymes involved in testosterone synthesis [47].