March 27, 2018
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Testosterone therapy in transgender men does not affect estradiol levels

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Transgender men treated with testosterone therapy did not experience increases in estradiol levels after 6 years of follow-up, but BMI decreased with increasing testosterone levels, according to findings published in Endocrine Practice.

“There are a lack of data on testosterone treatment in transgender men, both in regard to effect on estradiol levels and overall treatment efficacy,” the researchers wrote. “In non-transgender populations, there is reported concern for undesirable estrogenic effects in male-bodied individuals administered exogenous testosterone. Reports have also associated increased serum estradiol levels with risk of gynecomastia in males in general.”

Joshua D. Safer, MD, endocrinologist and medical director of the Center for Transgender Medicine and Surgery at Boston Medical Center, and colleagues evaluated 34 transgender men (median, 31 years) treated with testosterone to determine the effect of treatment on estradiol levels. Researchers were able to review 6 years of treatment with testosterone therapy.

Between baseline and several months after treatment initiation, testosterone levels rose (P < .0001). Steady-state levels were reached at 9 months, and no significant changes were observed for peak testosterone levels (mean, 650 ng/dL).

A decrease in estradiol level was observed with increasing testosterone level in a regression analysis (P < .02). However, over 6 years, no significant changes in estradiol levels were observed when steady-state testosterone levels were reached. A decrease in BMI was observed with increasing testosterone level (P < .05). Hematocrit also increased with increasing testosterone in a regression analysis (P < .05).

“Estradiol levels remain within the normal range in medically treated transgender men and do not rise,” the researchers wrote. “Thus, there is no evidence for elevated estradiol levels that may need to be mitigated with aromatase inhibitors. Further, we found no evidence of serum estradiol rise acting as added risk to female reproductive tissues in transgender men, although these data do not address intracellular aromatization of testosterone to estrogen.” – by Amber Cox

Disclosures: The authors report no relevant financial disclosures.