Hypothalamic-pituitary-testicular axis

Schematic representation of the hypothalamic-pituitary-testicular axis. GnRH from the hypothalamus stimulates the gonadotroph cells of the pituitary to secrete LH and FSH. LH stimulates the Leydig cells of the testes to secrete testosterone. The high concentration of testosterone within the testes is essential for spermatogenesis within the seminiferous tubules. FSH stimulates the Sertoli cells within the seminiferous tubules to make inhibin B, which also stimulates spermatogenesis. Testosterone inhibits GnRH secretion, and inhibin B inhibits FSH secretion.