Effect of a single injection of testosterone enanthate on 17\u3b2 estradiol and bone turnover markers in hypogonadal male patients.

PURPOSE: Several clinical studies testify the critical role played by estrogens in male bone metabolism. The aim of our study is to assess the effect of a single injection of testosterone enanthate in a group of hypogonadal men on 17\u3b2 estradiol serum levels and some bone metabolic parameters. METHOD: Twenty-one hypogonadal males were given one testosterone enanthate injection (250 mg). Blood samples were drawn before the injection and after 1, 2 and 3 weeks. The following variables were measured: Total testosterone (TT), 17\u3b2 estradiol (17\u3b2 E2), Sex hormone binding globulin, total alkaline phosphatase, osteocalcin, and C-telopeptide of type I collagen (CTx). RESULTS: After testosterone injection, both TT and 17\u3b2 E2 increased, peaking 1 week after the injection. Individual observation of the response of 17\u3b2 E2 to testosterone showed that a subgroup (n = 9) failed to respond with any increase in 17\u3b2 E2 at any of the weekly tests (group E2-), while the remainder (n = 12) showed a significant increase in 17\u3b2 E2, which reached a mean value three times higher than at baseline (group E2+). The E2- patients reached a TT peak lower than that observed in the E+ group. CTx serum levels declined progressively in the E2+ group, reaching the significance (p = 0.03) at the end of the study, while it did not change in E- group. CONCLUSION: This study suggests that a single injection of testosterone might have different effects on the production of endogenous estrogens, and a significant reduction of bone resorption parameters takes place only in the patients who show a significant increase of 17 f estradiol in response to testosterone administration