A systematic review of antiandrogens and feminization in transgender women.

Antiandrogens are frequently used with estradiol in transgender women seeking feminization. Antiandrogens act by various mechanisms to decrease the production or effects of testosterone, but it is unclear which antiandrogen is most effective at feminization. A systematic review was performed using PRISMA guidelines. We searched online databases (Medline, Embase and PsycINFO) and references of relevant articles for studies of antiandrogens in transgender women aged 16+ years to achieve feminization (namely changes in breast size, body composition, facial or body hair) or changes in serum total testosterone concentration when compared to placebo, estradiol alone or an alternative antiandrogen. Four studies fulfilled eligibility criteria and were included in a narrative review. The addition of cyproterone acetate, leuprolide and medroxyprogesterone acetate may be more effective than spironolactone or estradiol alone at suppressing the serum total testosterone concentration. Body composition changes appear similar in transgender women treated with estradiol and additional cyproterone acetate or leuprolide. No eligible studies adequately evaluated the effects of antiandrogens on breast development or facial and body hair reduction. It remains unclear which antiandrogen is most effective at achieving feminization. Cyproterone acetate, medroxyprogesterone acetate and leuprolide may be more effective than spironolactone at suppressing the serum total testosterone concentration. However, due to spironolactone's antagonism of the androgen receptor, it is unclear whether this results in clinically meaningful differences in feminization. Further research with clinically meaningful endpoints is needed to optimize the use of antiandrogens in transgender women.