| Abstract: | Scrum luteinizing hormone (LH), progesterone. 17β-estradiol, and testosterone were measured during a single cycle each of five female orangutans, and urinary LH was measured in four of those cycles. Midcycle peaks in LH and luteal phase elevations in progesterone (5.7–13.8 ng/ml) suggested that the cycles were ovulatory. 17β-Estradiol was elevated at midcycle (163–318 pg/ml) and during the luteal phase (56–136 pg/ml) and testosterone was also elevated at midcycle (143–580 pg/ml). These hormone patterns in the orangutans closely resemble those for chimpanzees, gorillas, and human females. |
