Male Reproductive System - Testosterone

• Under the influence of FSH and testosterone, Sertoli cells produce androgen-binding protein (ABP) that binds to testosterone and maintains high levels of the hormone near spermatogenic cells. • Testosterone stimulates the final stages of spermatogenesis. • In addition, testosterone is converted into to dihydrotestosterone (DHT), another hormone that may promote sperm cell formation. • Testosterone and DHT both bind to the same intranuclear receptors. • Together, the androgens regulate male prenatal development and the development of male sexual characteristics. • Male pattern of development (before birth) • Enlargement of male sex organs and expression of male secondary sex characteristics (starting at puberty) • Anabolism (protein synthesis) Negative feedback control of testosterone • Sertoli cells release the protein hormone inhibin when the level of spermatogenesis required for male reproductive functions has been attained. • Inhibin is delivered by the blood to the gonadotrophic cells within the anterior pituitary. • Inhibin acts on the gonadotrophs to reduce FSH secretion, decreasing the rate of spermatogenesis. • Similarly, testosterone acts in a negative feedback manner on anterior pituitary gonadotrophs to suppress the secretion of LH. • The negative feedback effect of testosterone also involves its effect on the hypothalamus, which results in decreased secretion of GnRH. • Decreased secretion of GnRH causes a corresponding decrease in the secretion of both LH and FSH. • The decrease in LH causes a decrease in the secretion of testosterone by the Leydig cells in the testes. • Low levels of testosterone reduce spermatogenesis. • Conversely, an excessive decrease in testosterone allows the hypothalamus to increase its secretion of GnRH. • This secretion causes an increase in anterior pituitary secretion of LH and FSH, and an increase in secretion of testosterone by the testes.

Add To

You must login to add videos to your playlists.