Gonadotropin-releasing hormone (GnRH) from the hypothalamus stimulates the anterior pituitary to secrete two hormones.

• Follicle-Stimulating Hormone (FSH) acts on Sertoli cells, which nourish developing sperm.

  Sertoli cells also secrete Inhibin, which reduces FSH secretion by negative feedback.

• Luteinizing Hormone (LH) acts on Leydig cells, which produce androgens, chiefly testosterone.

  Testosterone regulates production of the brain hormones by negative feedback.