Follicle-stimulating hormone (FSH) helps control the menstrual cycle and egg production in the ovaries. FSH also controls sperm production in the testicles. FSH is produced by the pituitary gland.

FSH levels normally vary throughout the menstrual cycle and are highest just before the release of an egg (ovulation). FSH levels for sperm production normally stay at a constant level. An abnormally high or low level of FSH is often a sign of an inability to produce eggs or sperm.