Estrogen induced enhancement of LHRH clearance in amenorrheic women.

In order to assess the effect of estrogen administration on LHRH metabolism in human plasma, plasma LHRH levels were determined in six amenorrheic women following iv injection of 500 ng synthetic LHRH before and after im injection of 5 mg estradiol benzoate (EB) for 4 days. The plasma levels of LHRH reached a maximum 1.25 min after LHRH administration, and they rapidly decreased in both situations. The initial disappearance of LHRH after EB treatment (half-life = 1.87 +/- 0.15 min) was significantly (p less than 0.05) more rapid than that before treatment (half-life = 2.45 +/- 0.21 min). The mean basal levels of plasma estradiol significantly (p less than 0.05) increased from 15.2 pg/ml to 4,387 pg/ml after EB treatment. Gonadotropin response to LHRH after EB treatment were not different from those before treatment. These data suggest that exogenous estrogen may stimulate the clearance of LHRH from the plasma of amenorrheic women.