Luteal Function in Hypophysectomized Rhesus Monkeys*

Experiments were designed to study the maintenance of corpus luteum function in the rhesus monkey. The experiments used a transfrontal microsurgical approach for total hypophysectomy. This proved to be a reliable and safe procedure for the complete removal of the pituitary gland. Luteal function was not affected by either complete hypophysectomy or sham surgery performed 1 day after ovulation. The concentrations of PRL in serum became undetectable during the luteal phase in hypophysectomized animals. Serum LH levels in the first postoperative cycle were detectable, but were just above the lower limits of sensitivity of the bioassay. Ovulation was induced with human menopausal gonadotropin and hCG or human menopausal gonadotropin and human LH at least 6 months after hypophysectomy, at which time endogenous LH was undetectable. These animals displayed normal luteal function, for approximately 10 days suggesting that the corpus luteum, once formed, can function independently of circulating LH and in the absence of the pituitary gland.