Effects of neutralization of luteinizing hormone on corpus luteum function and cyclicity in Macaca fascicularis

The primate corpus luteum (including the human) is thought to require continuous exposure to LH for normal progesterone production and menstrual cyclicity. Recently, normal luteal function was reported in rhesus monkeys after postovulatory hypophysectomy or treatment with an antagonist to GnRH. We studied the effects of neutralization of LH by specific antiserum in the fascicularis monkey. A potent antiserum to ovine LH, which cross-reacted with monkey pituitary extract, was produced in rabbits; this antiserum was administered daily to cycling monkeys during the midluteal phase. The pretreatment cycle duration was 32.4 +/- 1.7 (+/- SE) days, and luteal length was 16.5 +/- 0.8 days, with a midluteal progestin peak of 15.28 +/- 2.23 ng/ml. LH antiserum treatment resulted in a precipitous fall in serum progestin within 24 h, which remained low for the remainder of the cycle. All treated monkeys had premature menstrual bleeding, with mean cycle length shortened to 22.8 +/- 1.6 days (P less than 0.0005). These results confirm that the continuous presence of LH is essential for maintenance of corpus luteum function in this species of primate.