Further Studies of Gonadotropin and Estradiol Secretion During the Preovulatory Phase of the Human Menstrual Cycle1

The relationship between plasma estrogens and LH was studied in 13 normal menstrual cycles and compared to those reported in the literature, and data suggest that ovarian estradiol secretion is responsible for the midcycle LH peak and that LH may not exert immediate control over preovulatory est radiol secretion.

Abstract

The relationship between plasma estrogens and LH was studied in 13 normal menstrual cycles and compared to those reported in the literature. In 29 of 32 cycles the estradiol peak was found to occur within 48 hr prior to the LH peak, most commonly within 24 hr. Frequent blood sampling near the time of ovulation demonstrated, in some cases: a) a fall in estradiol concentration prior to significant LH changes, and b) a striking fluctuation in estrone and estradiol levels between successive samples. These data suggest that ovarian estradiol secretion is responsible for the midcycle LH peak and that LH may not exert immediate control over preovulatory estradiol secretion.