Hypothalamic-Pituitary-Gonadal (HPG) Axis

The Hypothalamic-Pituitary-Gonadal (HPG) Axis is an essential endocrine system network that plays a pivotal role in regulating reproductive health and the production of sex hormones. It begins with the hypothalamus, which releases gonadotropin-releasing hormone (GnRH). GnRH, in turn, stimulates the pituitary gland to secrete luteinizing hormone (LH) and follicle-stimulating hormone (FSH). LH and FSH then act on the gonads (testes in males and ovaries in females) to promote the production of sex hormones—testosterone in males and estrogen and progesterone in females—and gamete (sperm and egg) production. This axis is subject to intricate feedback mechanisms where sex hormones exert negative feedback on both the hypothalamus and pituitary gland to regulate hormone levels within a healthy range. Disruptions in the HPG axis can lead to various reproductive and hormonal disorders, including infertility, polycystic ovary syndrome (PCOS), and hypogonadism. Treatment strategies often involve hormonal therapies aimed at restoring the normal function of this axis.