Periovulatory Time Courses of Circulating Gonadotropic and Ovarian Hormones in the Rhesus Monkey1

Abstract

Samples of peripheral blood were taken from 4 intact rhesus monkeys every 3 hr for a 72–hr period encompassing the midcycle LH surge, and assayed for LH, FSH, estradiol, estrone and progesterone. The LH and FSH peaks were essentially parallel. They were continuous, symmetrical, and monophasic, with a mean duration of approximately 50 hr. The rate of decrease in LH concentration during the descending phase of the surge did not approach the half-life of LH in the monkey, indicating that secretion was continuing during this time. A sharp rise in estradiol accompanied the initial increase in LH, resulting in a peak which preceded that of LH by 9–15 hr. Progesterone was undetectable in peripheral plasma until 15 hr after LH began to rise, reaching a small peak within 6 hr of the LH peak. Estradiol started to decrease before the decrease in progesterone, but both steroids reached nadirs approximately 24 hr after the LH peak. In a separate group of 12 animals, the earliest evidence of ovulation was obtained approximately 28 hr after the LH peak. The mean time of ovulation was 37 hr after the LH peak. (Endocrinology93: 1140, 1973)