Sex hormones are steroidal hormones that determine both male and female sexual characteristics. The complex interaction of sex hormones is essential in sexual reproduction. Sex hormones consist of gonadotropin-releasing hormone (GnRH), follicle-stimulating hormone (FSH), luteinizing hormone (LH), estrogen, progesterone, prolactin, prostaglandins, androgens, and testosterone. The cyclic release of sex hormones begins in the hypothalamus situated near the pituitary gland, a pea-sized gland located at the base of the forebrain behind the bridge of the nose.

GnRH is pumped into blood vessels according to an extremely regulated pulse-pattern of the hypothalamus. During a woman's sexual cycle, the amount of GnRH released varies. Increased amounts of GnRH triggers the release of FSH and LH (known as gonadotropins) by the pituitary gland. In the male, FSH stimulates the formation of sperm in the testes; in the female, FSH stimulates a group of specialized cells which form a follicle surrounding...