Gonads: Ovarian and Testicular Hormones

I. Gonads - i. Ovaries : The gonads -- testes and ovaries -- besides producing gametes, also secrete their own hormones. The ovaries produce four: estrogen, secreted by the developing follicle (estradiol being the main form), responsible for female secondary sexual characters; progesterone, secreted by the corpus luteum after ovulation, essential for thickening the uterine endometrium to prepare it for implantation, for mammary gland development during pregnancy, and for inhibiting uterine contractions during pregnancy; relaxin, secreted by the corpus luteum at the end of gestation, which relaxes the cervix and the pelvic girdle's ligaments to ease birth; and inhibin, also secreted by the corpus luteum, which inhibits FSH and GnRH production. …