Effects of catechol estrogen infusions upon gonadotropin and prolactin concentrations in men

To study the effects of catechol estrogens upon gonadotropin secretion, 2-hydroxyestrone (2-OHE₁) and 2-hydroxyestradiol (2-OHE₂) were administered iv to young adult men in a range of doses for 4 days. Blood samples were obtained for plasma LH, FSH, and PRL at 20-min intervals for 6 h before and at the end of the infusion period. 2-OHE₁ had no effect upon gonadotropins or PRL in doses up to 1.6 mg/day; at 3.2 and 6.6 mg/day, it produced a slight suppression of LH and FSH, with no change in PRL. 2-OHE₂ was generally ineffective at 100 μg/ day, but doses from 200-800 μg/day supressed gonadotropins, without changes in PRL. These infusions elevated 2-OHE₁ and 2-OHE₂ plasma levels to values comparable to those measured in late pregnancy. There were no associated effects upon blood pressure and only minimal changes in urinary catecholamine excretion. No effects that could be interpreted as antiestrogenic were observed. These results are consistent with the hypothesis that circulating catechol estrogens behave as weak estrogens in men.