Hormonal synchronization of the menstrual cycles of pigtail macaques to facilitate biomedical research including modeling HIV susceptibility

Background Menstrual cycle synchronization of female pigtail macaques could prove an invaluable resource in studies of the reproductive tract, associated infections, and other potential research fields. We tested whether use of an oral progesterone and estradiol combination tablet could synchronize menstrual cycles following treatment discontinuation. Methods Daily desogestrel 0.075 mg and ethinyl estradiol 0.01 mg were administered orally to three pigtail macaques at visual onset of perineal sex swelling and were continued until all animals had received it for at least 45 days. The hormones were discontinued, and these three macaques and three controls were observed for menstruation and had blood progesterone and estrogen measured over an additional 2-month period. Results All treatment animals showed spontaneous menstrual cycle synchronization for 2 months after menstrual cycling resumed. Conclusion Progesterone and estradiol combination therapy can be used in pigtail macaques to induce synchronized cycling that persists in the absence of on-going hormone treatments.