The normal menstrual cycle is produced by a series of hormonal signals that starts with the release of gonadotropin-releasing hormone (GnRH) from the hypothalamus. The hypothalamus is located in the brain and is often referred to as the master gland. GnRH then acts on the pituitary gland and causes it to release two hormones, follicle stimulating hormone (FSH) and lutenizng hormone (LH). LH and FSH act on the ovary and cause it to release the hormones directly involved in menstruation, estrogen and progesterone.