Gonadotropin-releasing hormone from the hypothalamus is released in the portal system in order to reach the gonadotropic cells in the pituitary. Upon stimulation, these cells release FSH and LH. The Leydig cells in the testis carry receptors for LH. LH promotes the production of testosterone in these cells. Testosterone serves three main functions: it stimulates Sertoli cells
I LH stimulates the Leydig cells to produce testosterone and FSH stimulates the Sertoli cells to produce sperm cells. II Inhibin decreases secretion of FSH and LH by inhibiting GnRH secretion.
Extra info: Inhibin is an inhibitor of FSH synthesis and secretion.