Evidence that testosterone can suppress pituitary gonadotropin secretion independently of peripheral aromatization.
Testosterone (T) was given to normal men with and without the concomitant administration of the aromatase inhibitor, delta 1-testolactone (Teslac), to examine the role of peripheral aromatization of T in gonadotropin regulation. When T was administered alone by continuous iv infusion (15 mg/day for 4 days), serum T increased 3-fold (P less than 0.01) and estradiol (E) increased by 50% (P less than 0.01). These changes were associated with a 50% decrease in serum LH and FSH concentrations (P less than 0.01). When T was infused into men taking Teslac (2000 mg/day), serum T levels doubled (P less than 0.01), but E levels did not change (13.4 +/- 1.5 vs. 13.5 +/- 1.0 pg/ml; P = NS). This pattern of plasma steroids, increased T and unchanged E, was also associated with significantly decreased serum LH and FSH concentrations (14.5 +/- 0.4 vs. 8.0 + 0.4 mIU/ml and 9.9 +/- 2.5 vs. 5.8 +/- 0.1 mIU/ml, respectively; P less than 0.01). These data support the hypothesis that T or one of its metabolites can modulate LH and FSH secretion independently of peripheral aromatization to E.
D000328:Adult; D004958:Estradiol / Q000097:blood / Q000378:metabolism*; D005640:Follicle Stimulating Hormone / Q000097:blood* / Q000378:metabolism; D006801:Humans; D007986:Luteinizing Hormone / Q000097:blood* / Q000378:metabolism; D008297:Male; D013738:Testolactone / Q000494:pharmacology; D013739:Testosterone / Q000097:blood / Q000378:metabolism / Q000494:pharmacology*
D013739:Testosterone; D004958:Estradiol; D013738:Testolactone; D007986:Luteinizing Hormone; D005640:Follicle Stimulating Hormone