This is a potential side effect but is relatively rare if prescribed and used properly. Testosterone can convert into estradiol through a process called aromatization, which over time can cause gynecomastia, aka man boobs. (6) Clinically, I’ve seen this happen but only in older males that just take TRT and do not incorporate any lifestyle changes or exercise, particularly weight training. Patients that weight train tend to not experience this side effect. High estradiol levels from taking TRT is easily treated by adding in a very small dose of anastrozole once weekly to block estrogen conversion. This fixes the issue very quickly.