Follicle-stimulating hormone (FSH) helps control a woman's
menstrual cycle and egg production and also a man's sperm production. FSH is
produced by the pituitary gland.
Women's FSH levels normally vary throughout the menstrual cycle and
are highest just before release of an egg (ovulation). Men's FSH levels
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.