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Follicular Stimulation Versus OvulationInduction in Juvenile Primates: Importance of Gonadotropin-Releasing Hormone Dose

Department of Obstetrics and Gynecology, Keesler Medical Center/SGHSO Biloxi, Mississippi 39534
Department of Obstetrics and Gynecology, The Jones Institute for Reproductive Medicine, Eastern Virginia Medical School Norfolk, Virginia 23507
The Jones Institute for Reproductive Medicine, Eastern Virginia Medical School Norfolk, Virginia 23507

Address requests for reprints to: Dr. V. M. Sopelak, Department of Obstetrics and Gynecology, University of Mississippi Medical Center, 2500 North State Street, Jackson, Mississippi 39216.

We evaluated the dose of GnRH administered by 1-min pulsatile infusion necessary to achieve follicle growth vs. the dose needed for ovulaton induction. Doses of 6.0, 0.6, and 0.06 µg GnRH were given to juvenile monkeys iv in 1 min once per h for 4 consecutive months. Monkeys receiving hourly 6.0-µg doses of GnRH had cyclic elevations of serum estradiol and had menses, but did not ovulate, as evidenced by lack of a corpusluteum at laparoscopy and consistently low progesterone concentrations. These monkeys ovulated only when hCG was administered near midcycle as a surrogate LH surge. In contrast, monkeys receiving 0.6-µg doses of GnRH frequently had normalovulatory menstrual cycles and characteristic elevations of progesterone during the luteal phase. Typically, juvenile monkeysreceiving hourly 0.06-µg doses of GnRH initially had development of a dominant follicle contemporaneous with a rise ofserum estradiol, but never ovulated or had any subsequent follicular growth or elevated steroidogenic activity. In summary,ovarian follicular development and steroidogenesis in juvenile monkeys can be initiated by doses of GnRH ranging from 0.06–6.0 µ;g/h, although spontaneous ovulation and normal luteal function occurred frequently only with the 0.6 µg/h pulses of GnRH. Thus, the dose range of pulsatile GnRH needed for follicle growth is much broader than that required for induction of ovulatory menstrual cycles.

^* Supported in part by Ford Foundation Grant 810–0293 and NIH Biomedical Research Support Grant 2-S07-RR05386.

Received May 29, 1985.