The interrelationship between sex skin swelling and the urinary excretion of LH, estrone, and pregnanediol by the cycling female chimpanzee.

The interrelationship between sex skin swelling and the urinary excretion of luteinizing hormone and sex steroids was investigated during ovulatory menstrual cycles in adult female chimpanzees. Estrone was excreted in two peaks, one during the preovulatory and the other during the midluteal phase. Maximum swelling of the sex skin was attained several days before the preovulatory estrone peak. The LH surge preceded or accompanied beginning detumescence of the sex skin which, in turn, was closely correlated with a rising excretion of pregnanediol. Urinary measurements provide integrated estimates of the concentration of fluctuating hormones and, in addition, are safer and easier to make than blood measurements in this species.