Exposure to ovarian steroids elicits a female pattern of plasma cortisol levels in castrated male macaques.

Our recent observations (1) that there is a difference in circadian patterns of plasma cortisol levels between male and female macaques and (2) that after gonadectomy these differences in the patterns and in the levels of cortisol were reduced prompted us to investigate how 17 beta-estradiol (E2) and progesterone affect cortisol secretion in orchidectomized male rhesus macaques. Five male macaques, castrated as adults, were implanted subcutaneously with segments of silastic tubing filled with E2 and with progesterone in a manner such that the levels and the sequence of these hormones mimicked those that occur during the menstrual cycle of intact female macaques. Since previous studies had shown that the difference in cortisol patterns was due to higher levels in females during the day, these studies were conducted from 0800 to 2000 hours. Blood samples were collected in an adjacent room at 15-minute intervals. Separate trials were conducted 2 weeks after E2 was implanted and levels were 110 +/- 14 pg/ml and again 2 weeks later after progesterone was implanted and E2 levels were 59 +/- 15 pg/ml; progesterone levels averaged 4.0 +/- 0.65 ng/ml. Mean plasma concentrations of cortisol (microgram/100 ml) for the 12-hour period were three-fold higher in orchidectomized males treated with E2 (17.2) and with E2 + progesterone (18.0) than in intact males (4.9). Levels in males treated with ovarian steroids were double that (8.5 micrograms/100 ml) observed for intact females.(ABSTRACT TRUNCATED AT 250 WORDS)