Follicle-stimulating hormone, or FSH, is a hormone produced by the pituitary gland in the brain. It plays a crucial role in regulating the reproductive processes in both men and women. In women, FSH stimulates the growth of ovarian follicles, which are essential for egg development. In men, it supports the production of sperm. FSH levels fluctuate throughout the menstrual cycle in women, peaking just before ovulation. Abnormal levels of FSH can indicate various health issues, such as polycystic ovary syndrome or testicular dysfunction. Testing FSH levels can help diagnose reproductive health problems.