The Grapevine

Testosterone Therapy Does Not Increase Estrogen Levels In Transgender Men, Study Finds

The present guidelines for the treatment of transgender men using testosterone therapy state that there might be a need to include estrogen-lowering strategies such as the removal of the uterus or ovaries. But a new study led by Boston Medical Center (BMC) suggests that testosterone therapy is not linked to increased estrogen levels among transgender men.

The paper titled 'Estrogen Levels Do Not Rise With Testosterone Treatment For Transgender Men' was published online in Endocrine Practice. Joshua Safer, MD, endocrinologist and former medical director of the Center for Transgender Medicine and Surgery at Boston Medical Center conducted the study with colleagues.

"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," the study stated.

Over a six-year period, researchers followed the health of 34 transgender men who were undergoing testosterone therapy at the Endocrinology Clinic at Boston Medical Center. Estradiol levels were extracted in an anonymized manner from the electronic medical records. Most of the patients had just started the treatment when the study began, allowing the comparison of baseline estrogen levels. Testosterone and estrogen levels were checked every six months with the exception of the first year of the study when they were checked every six months.  

According to the findings, no rise in estrogen levels was observed among the transgender men. In a regression analysis, it appears that the patients actually experienced an initial decline in estrogen along with increasing testosterone levels. The estrogen levels eventually stabilized and remained within the normal range. Data also showed an increase in red blood cell count and a decrease in Body Mass Index (BMI). The study suggests that the latter may have played a role in contributing to the fall in estradiol levels.

"There are no nationally representative data sets to prove the efficacy of hormone therapy," Dr. Safer said. "Clinic-based studies like this can inform best-practice recommendations and help transgender men feel confident in the safety of their care."

High levels of estrogen have been associated with certain health risks such as thyroid dysfunction, endometrial cancer, pelvic pain, blood clots and stroke. 

"Estradiol levels remain within the normal range in medically treated transgender men and do not rise," the authors of the study 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."

This is the first study to examine how estrogen levels react in response to testosterone therapy in transgender men over an extended period of time. Endocrinologists have previously expressed that there is a significant lack of such data, leaving them with a lot of questions regarding the safety, benefits, and risks of hormone therapy.