Figure 1.

Twenty-four-hour plasma profiles of adrenal steroids in male and female rhesus macaques. Serial blood samples were remotely collected from adult (11–12 years) male (n = 10) and female (n = 8) animals and assayed for cortisol (A) and DHEAS (B). Each data point represents the mean and vertical lines indicate the SEM. Time of day is indicated along the abscissa, and periods of darkness and light are represented by black and white bars, respectively. In both sexes, cortisol and DHEAS levels rose gradually during the night and reached peak levels around the time of lights on in the morning. Mean cortisol levels were similar in the two sexes, whereas mean DHEAS levels were significantly higher in males than in females (P < 0.01, Student’s t-test.)