Hormonal pathways that influence sperm formation

Negative feedback loops control hormonal secretion by the hypothalamus, the anterior lobe of the pituitary gland, and the testes.

1. Level of testosterone in blood declines; hypothalamus secretes GnRH.
2. GnRH stimulates secretion of LH,FSH from anterior lobe of pituitary
3. LH prompts Leydig cells in testes to produce and release testosterone.
4. Sertoli cells bind FSH andtestosterone, and function inspermatogenesis at puberty.
5. Testosterone and secretions from Sertoli cells encourage sperm production.
6. Elevated level of testosterone in blood inhibits secretion of GnRH.
7. Elevated level of testosterone in blood causes Sertoli cells to release inhibin, which inhibits FSH secretion.