The late pubertal cascade in perimenarchial monkeys: onset of asymmetrical ovarian estradiol secretion and bioassayable luteinizing hormone release.

Changes in ovarian function and pituitary gonadotropin secretion were studied in perimenarchial rhesus monkeys. Even in the premenarchial interval, a modest degree of asymmetrical ovarian estradiol secretion was evident. A progression toward marked asymmetry of ovarian function continued after menarche, culminating in ovulatory menstrual cycles with intermenstrual intervals of approximately 28 days. Among postmenarchial monkeys manifesting five or fewer episodes of overt uterine bleeding, no ovulations were detected despite estradiol elevations similar to those of adults in the midfollicular phase. Soon thereafter, among individuals usually having more than 10 menses, the first ovulations were likely to be achieved. The initiation of estrogen-positive feedback, driving the surge modes of gonadotropin secretion, was accompanied by the onset of a striking disparity between bioassayable vs. immunoassayable LH in the circulation. In this report we describe a cascade of late pubertal events including: 1) the gradual establishment of cyclic asymmetrical ovarian estrogen secretion in the perimenarchial interval, 2) increased pituitary responsiveness to GnRH, 3) quantitative and qualitative changes in the pulsatile secretion of pituitary gonadotropins, and 4) an enhancement of bioassayable LH secretion, especially during the preovulatory surge.