Plasma androgens during early pregnancy in the baboon (Papio cynocephalus)

Time-mated baboons (n = 8) were bled throughout the luteal phase of the cycle of conception, and an equal number of nonpregnant animals were studied as controls. A significant increase in plasma testosterone and androstenedione was seen in the cycle of conception prior to expected menses, whereas the levels in nonpregnant baboons were unchanged throughout the luteal phase. Plasma testosterone and androstenedione continued their rise in three pregnant baboons sampled between days 16 and 33 of gestation. In an additional three baboons bled at 4-day intervals from day 35 through day 75, there was a further increase to about day 40, but by day 50 the androgen levels had declined to nonpregnant luteal phase levels and remained constant. Treatment with human chorionic gonadotropin during the nonpregnant luteal phase caused increases in both testosterone and androstenedione. Removal of the ovary bearing the corpus luteum at day 20 of gestation resulted in abortion and a sharp drop in plasma progesterone and estradiol. One baboon had a dramatic decline of the elevated plasma androgen following oophorectomy, while another that did not have elevated androgen levels showed only a trivial decline. Pregnancy continued in two baboons in which the corpus luteum-bearing ovary was removed at day 25 or day 30. There was only a slight drop in plasma progesterone postoperatively and a rapid return to normal levels. A similar decline, with a more gradual recovery, was noted in plasma estradiol and androgen levels. In one animal the androgen levels were increased by about day 40 and subsequently declined by day 50, just as did the androgens of unoperated pregnant baboons. Estrogen administration in early pregnancy causes a suppression of the normal increases in plasma estradiol and androgen levels.