Follicle-stimulating hormone (FSH) is a hormone produced by the pituitary gland in the brain. It plays a crucial role in regulating the reproductive processes in both males and females. In women, FSH stimulates the growth and maturation of ovarian follicles, which are essential for egg development. In men, it supports the production of sperm in the testes. FSH levels fluctuate throughout the menstrual cycle in women and are important for fertility. Abnormal levels of FSH can indicate various health issues, including polycystic ovary syndrome (PCOS) in women or hypogonadism in men, affecting reproductive health and overall well-being.