Male Hormones STUDENT VERSION PDF

MALE HORMONES Dr. Mariana flores MD, MSc [email protected] Objectives Review the functions of the male reproductive system. Know spermatogenesis and its hormonal regulation Identify all the hormones produced in the reproductive system, where are they produced, and their regulatory axis. Un...

MALE HORMONES Dr. Mariana flores MD, MSc [email protected] Objectives Review the functions of the male reproductive system. Know spermatogenesis and its hormonal regulation Identify all the hormones produced in the reproductive system, where are they produced, and their regulatory axis. Understand the effects and importance of all male hormones produced in the reproductive system Know generalities of hypergonadism and hypogonadism. Reproductive functions of the male Male Hormones Male Sexual Act Spermatogenesis Spermatogenesis Spermatogenesis LH GH T ES TO S T E RO N E FSH Sertoli cells ESTROGEN SPERMIOGENESIS Male Hormones Gonadotropic Hormones: LH & FSH Testosterone LH testosterone production Secretion is regulated by (Gonadotropin-releasing hormone) GnRH (↑ GnRH = ↑ LH) Cyclic fashion (1-3h) Is directly and indirectly inhibited by testosterone (↑Test. = ↓LH & ↓GnRH) Acts on Leydig cells to increase LH Acts on Leydig cells to increase testosterone production Glycoprotein: Activating the cAMP 2nd messenger system ACUTE EFFECTS: StAR y esterases TROFIC EFFECTS: Increases expression of steroidogenic enzymes. Stimulates cholesterol synthesis. Increases receptors for expression of LDL receptors. 3𝛽 −hydroxysteroid dehydrigenase FSH Acts on Sertoli cells to activate spermatogenesis Secretion is regulated by GnRH: (↑in GnRH = ↑ in FSH). General levels over longer periods of time. Is directly and indirectly inhibited by Inhibin: (↑Inhibin = ↓FSH & ↓GnRH) FSH Glycoprotein: Activating the cAMP 2nd messenger system. Inhibin B & Activin A: Inhibin B → negative feedback mechanism to FSH production in the anterior pituitary. Activin A → CONTROL INFAMATION/FRIBROSIS/IMMUNITY + fine control of the cycle of the seminiferous epithelium Elevated activin A during inflammation and infection may contribute to spermatogenic failure, fibrosis and testicular damage Low levels of inhibin (& high FSH) are linked to infertility What is the most biologically relevant and irreplaceable function of AMH? AMH = antimüllerian hormone Hypothalamic-Pituitary-Gonadal Axis Hypothalamus→ GnRH (Gonadotropin Releasing Hormone) Pituitary (Gonadotropes)→ LH (Luteinizing Hormone) FSH (Follicle-Stimulating Hormone) Testes→ Leydig cells: Testosterone (LH) Sertoli Cells: Spermatogenesis (FSH) Estrogens Small amounts are formed in the male (about one-fifth the amount in the nonpregnant female). The exact source of estrogens →unclear. (1) The concentration of estrogens in the fluid of the seminiferous tubules is relatively high and probably plays a vital role in spermiogenesis. (2) Believed to be formed by the Sertoli cells by converting testosterone to estradiol. (3) Much more significant amounts of estrogens are formed from testosterone and androstanediol in other tissues of the body→ liver. TESTOSTERONE Testes produce testosterone, dihydrotestosterone, and androstenedione AKA androgens. Any steroid hormone that has masculinizing effects Most important one: Testosterone Potency of effects: Dihydrotestosterone (DHT) > Testosterone > Androstenedione Testosterone secretion Leydig cells (non-germ cells): Produce Testosterone. Almost inexistent in children. Newborns and post-puberal males: testes secrete large quantities of testosterone. Tumor = ↑ testosterone. As non-germ cells, usually continue to produce testosterone after x-rays or heat. Adrenal glands: