Effect of a gonadotropin-releasing hormone agonist and gonadotropins on ovarian follicles in cynomolgus monkey: a model for human ovarian hyperstimulation

STUDY OBJECTIVE: To examine the effect on large follicles (greater than or equal to 2 mm) of human menopausal gonadotropin (hMG) and buserelin acetate, a gonadotropin-releasing hormone agonist in monkeys. DESIGN: Experimental. SETTING: Reproductive research laboratory. ANIMALS: Fourteen cyclic cynomolgus monkeys receiving hMG alone for 8 days or buserelin acetate plus 8 (group 1), 12 (group 2), or 16 (group 3) days of hMG administration always starting from day 1 of the cycle. RESULTS: The different treatments were effective in over-riding the specific ovulatory quota of 1, and more large follicles developed in treatments involving long duration and higher doses of hMG. In buserelin acetate plus hMG treatments, the frequency of dissociated follicles and follicles in late atresia were, respectively, lower and higher than in hMG alone treatment. The numbers of recoverable mature oocytes (germinal vesicle breakdown) were similar to the numbers of such oocytes recovered after hyperstimulation performed for human in vitro fertilization and embryo transfer (IVF-ET). However, the number of mature oocytes enclosed in typically preovulatory follicles was very low because there were numerous dysmature follicles. CONCLUSION: These data suggest a deleterious effect of buserelin acetate plus hMG treatments on the recruitable follicles at the time when treatments start. The implications of these observations in the field of human IVF-ET are discussed.