Cumulative ovulation rate in human menopausal/human chorionic gonadotropin-treated monkeys: "step-up" versus "step-down" dose regimens

Cumulative ovulation rates in monkeys given human menopausal gonadotropin/human chorionic gonadotropin (hMG/hCG) on menstrual cycle days 3 to 9 in a "step-up" versus "step-down" protocol were compared with those achieved by hMG only. Using direct ovarian observation to detect sites of follicular rupture, retrograde tubal irrigation to collect eggs or embryos, and serum estradiol and progesterone levels to infer changes in ovarian status, we counted the number of ovulations at intervals of 24, 48, 72, 96, and 120 hours after hCG or comparable intervals without hCG. The data indicate (1) whereas most ovulations occurred on or before day 3 after hCG treatment, when the "step-up" dose regimen was employed additional follicles had ruptured on days 4 and 5; (2) a "step-down" protocol for hMG therapy may better synchronize follicular rupture and reduce susceptibility to delayed ovulations compared with a "step-up" dose regimen; and (3) under hMG stimulation, few follicles would rupture spontaneously (without hCG or luteinizing hormone treatment).