The negative feedback control by estradiol and progesterone of LH secretion in the ovariectomized rhesus monkey.

The pulsatile, circhoral discharges of LH observed in ovariectomized rhesus monkeys were blocked within min following single intravenous injections of 17β-estradiol or the initiation of estradiol infusions which achieved physiologic plasma levels of the steroid. The resulting depression in plasma LH concentrations was maintained for several hr after circulating estrogen levels had declined to undetectable values. Pulsatile LH discharges resumed abruptly following this period of inhibition but with a lower frequency and larger magnitude. In contrast, intravenous injections of progesterone had no effect on LH secretion unless massive doses were given, with resultant plasma concentrations of the steroid a thousand fold greater than luteal phase levels. These but caused irregularities in the circhoral rhythm. Similarly, the daily subcutaneous administration of progesterone, in oil, for 2 weeks failed to reduce the elevated plasma LH concentrations in ovariectomized animals. It is concluded that estrogen is th...