Ovarian follicular development stimulated by leuprorelin acetate plus human menopausal gonadotropin in chimpanzees

We attempted ovarian stimulation using gonadotropins in 14 chimpanzees. Subjects were given a single administration of leuprorelin acetate, followed by repeated administration of human menopausal gonadotropin (hMG) for 16-21 days. During the dosing period, the ovarian follicle diameter and count were measured by transvaginal ultrasonography. The hormone administration induced the development of multiple follicles, and multiple oocytes were subsequently retrieved. However, the follicle count was decreased, suggesting atresia, in some subjects. Statistically, the final follicle diameter was dependent on the dosing duration and the hMG dose in the late stage, while the maximum follicle count during hMG administration was dependent on age and the hMG dose in the early stage. Five subjects showed mild ovarian hyperstimulation syndrome (OHSS)-like symptoms with a high serum estradiol (E2) concentration. These results suggest that leuprorelin acetate plus hMG administration successfully stimulates the development of multiple ovarian follicles for oocyte retrieval and that the serum E2 concentration is predictive of OHSS-like symptoms in chimpanzees.