| Abstract: | To determine the effects of a human oral contraceptive on normal and abnormal reproductive endocrine patterns in two lowland gorillas (Gorilla gorilla), daily urine samples were analyzed by radioimmunoassay for estrone conjugates (EC) and pregnanediol-3-glucuronide (PdG). During a pre-treatment period one female (F1) demonstrated regular menstrual cycles averaging 27.6 ± 1.8 days, whereas ovarian cyclicity in female 2 (F2) was consistently prolonged, ranging from 37–51 days. A 56 day regimen of an oral contraceptive (Demulen 50®) was administered to both females beginning in the late luteal phase, and within 6 and 7 days of treatment onset (F1 and F2, respectively) urinary EC and PdG declined to and remained at concentrations consistent with amenorrhea throughout the administration period. Ten and twenty days after contraceptive withdrawal (F1 and F2, respectively) an EC peak was observed with subsequent PdG elevations 1–2 days later. Mean cycle length and luteal phase durations were not different (P > 0.05) before or after treatment for either female, while combined peak PdG concentrations were greater (P < 0.05) for the first 3 months after treatment compared to pre-treatment values. These results indicate that a human oral contraceptive rapidly suppresses ovarian activity in female lowland gorillas, but that the abnormal endocrine pattern observed in F2 could not be redirected into a normal profile after contraceptive withdrawal. © 1992 Wiley-Liss Inc. |
