The gonadal hormones, secreted primarily by the ovaries and testes, include estrogens, progesterone, and testosterone. These hormones are essential for normal sexual development and reproductive function in men and women. All gonadal hormones are steroids, and their molecular structures and those of the adrenocorticosteroids are quite similar. Moreover, small amounts of the gonadal hormones or precursors thereof are secreted by the adrenal glands in both men and women.
Secretion of gonadal hormones is regulated via the hypothalamic-hypophyseal system. When blood levels of gonadal hormones decline, the hypothalamus is stimulated to release gonadotropin-releasing hormone, which then stimulates the adenohypophysis to release its gonadotropic hormones. These tropic hormones are called, in both men and women, follicle-stimulating hormone and luteinizing hormone, even though the ovarian follicle and corpus luteum are unique to women.