Anti-Androgenic Effects Comparison Between Cyproterone Acetate and Spironolactone in Transgender Women: A Randomized Controlled Trial

Abstract

Background: Spironolactone and cyproterone acetate are commonly used in feminizing hormone therapy to achieve the goal of female range testosterone level; however, the data on the efficacy comparing between these two anti-androgens are scarce.

Aim: To compare the anti-androgenic effects between spironolactone and cyproterone acetate as the component of feminizing hormone therapy among transgender women population.

Methods: The study was single-blinded randomized controlled trial involved 52 transgender women from two transgender health clinics. Each participant received oral estradiol valerate 4 mg/day combined with anti-androgen, spironolactone 100 mg/day or cyproterone acetate 25 mg/day, depending on which group they were randomized to. Clinical and biochemical variables were obtained at baseline and at 12 weeks of feminizing hormone therapy.

Main outcome measures: The change of testosterone level from baseline. Other changes including free testosterone, estradiol, prolactin and lipid profile after the therapy.

Results: After a 12 weeks of feminizing hormone therapy, the change of testosterone level in the cyproterone acetate group [558.0 ng/dL (IQR 352.0 to 783.3)] was significantly higher than the spironolactone group [226.2 ng/dL (IQR,-4.3 to 480.1)](p value <0.001). Testosterone and calculated free testosterone in the cyproterone acetate group were significantly lower than the spironolactone group. Consequently, a proportion of the participants who achieved the female range testosterone (<50 ng/dL) was significantly higher in cyproterone acetate group (90%) compared to the spironolactone group (19%). Serious adverse effects observed in cyproterone acetate users were drug-induced liver injury and asymptomatic hyperprolactinemia.

Clinical implications: The data on the differences between the two anti-androgen could be benefit for the transgender health-care providers in medication selection and adverse-effects counseling.

Strengths & limitations: The study design was randomized controlled trial and controlled the estrogen component by prescribed the same type and dose for each participant. However, the study was suffered from the confound feminizing effects from previous hormone therapy and the high drop-out rate.

Conclusion: For feminizing hormone therapy, cyproterone acetate had a higher testosterone suppression efficacy than spironolactone. Burinkul S, Panyakhamlerd K, Suwan A, et al. Anti-Andorgenic Effects Comparison Between Cyproterone Acetate and Spironolactone in Transgender Women: A Randomized Controlled Trial. J Sex Med 2021;18:1299-1307.

Keywords: Androgen antagonists; Cyproterone acetate; Feminizing hormone therapy; Gender dysphoria; Spironolactone; Transgender persons.