The follicle stimulating hormone, or FSH, is a heterodimeric glycoprotein which acts on spermatogonia in males and stimulates the production of sperm in sexually mature males. FSH is a gonadotropin which, together with the other gonadotropin known as the luteinizing hormone, or LH, produces male gametes in the testis. The action of FSH in males, together with testosterone, stimulates all the phases of spermatogenesis.
The hypothalamus is a part of the brain which connects to the pituitary gland and regulates the production and secretion of ganadotropin releasing hormone or GnRH. GnRh is responsible for the production and release of FSH and LH. FSH in males binds to specific receptors on Sertoli cells found within the testis which manufacture a product called inhibin. A decreased production of inhibin is associated with a decrease in spermatogenesis. Sertolli cells are produced in the seminiferous tubule within the testicle. They are activated by FSH in males and are responsible for excreting substances which trigger phases of development of the spermatozoa.
The pituitary gland is located at the base of the brain and consists of the anterior and posterior lobes. There are six types of secretory cells in the anterior lobe which secrete hormones in response to signals from the hypothalamus. These include FSH and LH, both of which are responsible for reproduction in males and females. In males, FSH is critical for the production of sperm and in females it acts on the follicle to stimulate the release of estrogens.
In cases of infertility, levels of FSH are used to aid in determining the reason for a low sperm count. High levels are due to primary testicular failure which may be the result of developmental defects in testicular growth or injury to the testes because of a viral infection such as mumps, radiation or chemotherapy and trauma. Pituitary or hypothalamic disorders may cause low levels of FSH in males.
When a doctor suspects that a child is experiencing delayed or early sexual maturation, they may order an FSH test to evaluate pituitary function. FSH levels are normally high after birth but fall soon after, maintaining a low level until shortly before the beginning of puberty. Puberty is usually triggered by the hypothalamus signaling the pituitary gland to release hormones. An irregular onset of puberty may be an indication of a more serious problem in the hypothalamus or pituitary gland and the measurement of FSH and LH can differentiate between benign symptoms and an actual medical condition.