Bicalutamide does not raise transaminases in comparison to alternative anti-androgen regimens among transfeminine adolescents and young adults: a retrospective cohort study

BackgroundBicalutamide is a potential anti-androgen for transgender individuals with feminizing embodiment goals, but use has been limited because of hepatotoxicity in cisgender men with prostate cancer. This study compared transaminase changes in transfeminine adolescents and young adults (AYA) using low-dose bicalutamide with individuals using other methods of androgen blockade. MethodsA retrospective analysis was conducted using electronic health record data for patients starting gender affirming hormone therapy with at least 10 months of follow-up data between 2015 and 2023. Linear mixed models compared change in ALT and AST from baseline and maximum ALT and AST values in bicalutamide and comparison groups. Secondary outcomes included % individuals with ALT and AST elevation more than 1, 2, or 3 times the upper limit of normal (ULN) (Fishers exact test), standardized mean estradiol dose by group (t test), and Tanner staging of breast tissue by group (Fishers exact test). ResultsEighty-four transfeminine AYA (median age 18) taking bicalutamide were compared to 69 transfeminine AYA (median age 19) taking GnRH agonists, spironolactone or no agent in addition to estradiol. In linear mixed models adjusted for baseline age, BMI, baseline ALT or AST, and alcohol use, there was no difference in delta or maximum ALT or AST in bicalutamide and comparison groups. No individuals had an AST or ALT level > 3x ULN. Estradiol doses and Tanner stages were similar between groups in a subgroup analysis of individuals receiving pediatric care. ConclusionBicalutamide was not associated with significant change in transaminases as compared with other anti-androgen regimens over one year. Bicalutamide appears to be a safe anti-androgen for transfeminine individuals at low dose with close monitoring and deserves further study.