Luteinizing hormone: A gonadotropin (a hormone that affects the function of the sex organs) that is released by the pituitary gland in response to luteinizing hormone-releasing hormone. Abbrevi'ated LH. In females, LH controls the length and sequence of the female menstrual cycle, including ovulation, preparation of the uterus for implantation of a fertilized egg, and ovarian production of both estrogen and progesterone. In males, LH stimulates the testes to produce androgen. Also known as interstitial-cell-stimulating hormone (ICSH). See also gonadotropin.