Follicle-stimulating hormone (FSH) is an important part of the reproductive system and its responsibility includes the growth of ovarian follicles. Estrogen and progesterone in the ovaries are produced by follicles, which also help in the maintenance of the menstrual cycles in women. In men, FSH is a part of the development of the gonads as well as sperm production. The FSH test measures the level of FSH found in your blood. Your doctor will order an FSH test to find the underlying cause of symptoms affecting the reproductive system. An FSH test is a simple blood test. Women might be asked to have this test done at a specific point in their menstrual cycle, usually the first couple of days.