Hormonal Control of Male Reproductive Functions • Hormones are secreted by: • Hypothalamus • Anterior pituitary gland • Testes • Functions: • Development of sperm cells • Development of secondary sex characteristics
Hypothalamic and Pituitary Hormones • Hypothalamus secretes gonadotropin-releasing hormone (GnRH) to anterior pituitary gland • In response, anterior pituitary gland secretes gonadotropins: • Luteinizing hormone (LH) • Follicle-stimulating hormone (FSH), aka interstitial cell-stimulating hormone (ICSH)
Hypothalamic and Pituitary Hormones, continued….. • FSH (ICSH) promotes development of ___________. • Testicular interstitial cells secrete male sex hormones. • LH stimulates supporting cells of seminiferous tubules to respond to testosterone.
Hypothalamic and Pituitary Hormones, continued….. • FSH + testosterone + supporting cells stimulate spermatogenic cells to give rise to ______________. • Supporting cells secrete inhibin, a hormone which inhibits the anterior pituitary gland, preventing secretion of FSH.
Male Sex Hormones • Called “Androgens” (???) • Where are they produced? • Most in testicular interstitial cells, but small amounts in adrenal cortex • What is the main male sex hormone? • Testosterone production begins before birth, continues a few weeks after, and then ceases until puberty.
Actions of Testosterone • Stimulates enlargement of testes and male accessory organs • Stimulates development of male secondary sex characteristics: • Increased growth of body hair • Enlargement of the larynx and thickening of the vocal cords • Thickening of the skin • Muscle growth, widening of shoulders, narrowing of waist • Thickening and strengthening of bones
Actions of Testosterone, continued….. • Increases rate of cellular metabolism • Increases rate of RBC production
Regulation of Male Sex Hormones • More testosterone = more developed secondary sex characteristics • Increased levels of testosterone inhibit the hypothalamus. • What effects would inhibition of the hypothalamus have?