Final answer:
Testosterone regulates sperm production through a negative feedback loop involving GnRH, FSH, and LH. High levels of testosterone and inhibin decrease the production of these hormones, slowing spermatogenesis, while low levels of sperm or inhibin will initiate an increase in sperm production.
Step-by-step explanation:
Testosterone regulation of sperm production is a critical aspect of the male reproductive system, operating through a precise negative feedback system. Spermatogenesis, the production of sperm, is influenced by hormones such as follicle-stimulating hormone (FSH) and luteinizing hormone (LH) which are controlled by the release of gonadotropin-releasing hormone (GnRH) from the hypothalamus. FSH stimulates Sertoli cells in the testes to promote sperm development, whereas LH induces Leydig cells to produce testosterone. When testosterone levels are sufficiently high, they exert a negative feedback effect on the hypothalamus and anterior pituitary, inhibiting the release of GnRH, FSH, and LH thereby reducing the production of testosterone itself and slowing down spermatogenesis. Concurrently, Sertoli cells secrete inhibin when sperm counts are high, which further reduces the release of GnRH and FSH and thus sperm production.
When sperm counts drop to a certain level, inhibin production decreases, allowing for an increase in sperm production. Leydig cells in the testes generate about 6 to 7 mg of testosterone per day, which is vital not only for the production of sperm but also for attributes such as muscle development, bone growth development of secondary sex characteristics, and maintenance of libido. In both males and females, testosterone plays different roles beyond the reproductive system.