Direct evidence in men for a role of endogenous oestrogens on gonadotrophin release

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Abstract
In 6 healthy subjects serum estradiol was selectively decreased by administering an aromatase activity inhibitor, hydrotestolactone (HT). After HT administration serum estradiol (E2) decreased from 18.7 .+-. 2.3 (SEM [standard error of the mean]) to 6.7 .+-. 0.6 pg/ml, whereas testosterone (T) and dihydrotestosterone blood levels were not modified. These E2 changes were associated with a singificant increase in serum LH [luteinizing hormone] and FSH [follicle stimulating hormone] concentrations (P < 0.001). Tamoxifen administration an estrogen antagonist, to 5 subjects caused a sharp increase in LH and FSH levels (P < 0.001). E2 was unchanged after the treatment with tamoxifen, whereas T levels were significantly higher. Apparently estradiol under physiological conditions plays a specific role in the feedback mechanism of gonadotropin release.