Ovarian hormone concentrations and genital swelling patterns in female chimpanzees with Norplant implants

Abstract

The purpose of this study was to assess the effects of Norplant implants on ovarian hormone secretion and genital swelling patterns in female chimpanzees. Urine samples were collected during one natural cycle before (n = 5 females) and one cycle ∼6 months following (n = 7 females) insertion of Norplant implants. Genital swelling data were recorded daily for all seven females. During Norplant treatment, two females exhibited minimal ovarian activity consistent with anovulation. Hormone data from five subjects indicated both follicular and luteal activity, suggesting that ovulation may have occurred during Norplant treatment. Among cycles presumed to be ovulatory, the concentration of estrone glucuronide did not differ from concentrations during the control phase. However, mean (F = 12.253, P = 0.001) and peak (F = 4.127, P = 0.003) concentrations of pregnanediol glucuronide were significantly lower during Norplant treatment. Cycle duration did not differ during Norplant treatment (F = 1.415, P = 0.200); however, duration of the total swelling phase (F = 3.311, P = 0.0011) and full swelling phase was shorter (F = 5.906, P = 0.011), whereas number of days with partial swelling increased (F = 2.635, P = 0.011). The results of this study indicate that Norplant provided effective contraception while not inhibiting ovarian hormone secretion or the expression of cyclic genital swelling in the majority of the chimpanzee subjects. Zoo Biol 16:209–223, 1997. © 1997 Wiley-Liss, Inc.