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: 1.Luteinizing hormone (LH) 2.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: 1.Increased growth of body hair 2.Enlargement of the larynx and thickening of the vocal cords 3.Thickening of the skin 4.Muscle growth, widening of shoulders, narrowing of waist 5.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?