Hormone Levels and Anogenital Swelling of Female Chimpanzees as a Function of Estrogen Dosage in a Combined Oral Contraceptive

Abstract

Abstract

A combined oral contraceptive consisting of ethinyl estradiol (EE₂) in three dosages (50, 100, and 400 μg) and norethindrone (0.5 mg) was given to female chimpanzees to determine the effect on endogenous sex hormone levels and anogenital swelling. Serum levels of EE₂ increased with increasing dosages of EE₂, estradiol decreased, and luteinizing hormone, progesterone and testosterone were maintained at approximately midfollicular phase levels. Urinary levels of EE₂ glucuronide increased with the increasing dosages of EE₂, whereas estrone and pregnanediol glucuronide were essentially undetectable. The cyclic increase in female anogenital swelling was abolished when the norethindrone was combined with 50 μg of EE₂ and relatively constant and low levels of swelling were recorded. Relatively constant but successively higher levels of swelling were recorded when the norethindrone was combined with the higher dosages of EE₂. These effects of oral contraceptives on female genital tissues are relevant to our laboratory studies of sexual behavior in chimpanzees given oral contraceptives and could also have some implications for women taking oral contraceptives.