P194 VERY LOW-DOSE CYPROTERONE ACETATE (12.5 MG/DAY) IS EFFECTIVE AS ANDROGEN BLOCKER; WELL TOLERATED AND NOT ASSOCIATED WITH HYPERTENSION DEVELOPMENT IN YOUNG FEMALE TRANSGENDER PEOPLE

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Background and Objective: Cyproterone acetate (CPA) has serious adverse effects (hyperprolactinemia, obesity, depression, thrombogenesis, liver toxicity, meningioma…) but the optimal dose has not been established. CPA is associated with a high risk of hypertension development, even with doses as low as 25 mg/day. We sought to establish if a very low CPA dose (12.5 mg/day) is effective as antiandrogen, its side effect profile, and if it is associated with hypertension development. Methods: Consecutive non-orchidectomized transgender women <30 years were offered CPA 12.5 mg/day instead of the regular 50-100 mg/day dose, along with estradiol (individually titrated); CPA dose was increased to 25 (eventually 50) mg/day if plasma testosterone was >2 nmol/L or there was clinical hyperandrogenism. Body weight, blood pressure, AST, ALT, GGT, prolactin, FSH, LH, estradiol and testosterone were monitored. A matched group of patients with LHRH agonist as antiandrogen plus estradiol served as control. Hypertension was diagnosed according to the current ESH guidelines. All patients gave informed consent. Results: 39 patients were recruited, median follow-up was 2.3 years. 32 were maintained on CPA 12.5 mg/day, two increased to 25 mg/day, one to 50 mg/day, two withdrew due to gender-affirming surgery; one was lost to follow-up. There were no serious side effects or related withdrawals. The control group included 35 patients without significant differences at baseline. Suppression of testosterone, LH and FSH were effective and comparable with the control group but a moderate increase in prolactin was observed (26±12 to 38±22 ng/mL, p=0.034). Neither group had changes in liver enzymes. Blood pressure and body weight did not increase significantly in either group; the incidence of hypertension was low in both groups (1 patient each). Conclusions: Very low-dose CPA was effective and well tolerated as antiandrogen in a large majority of our patients. While CPA is reportedly associated with a striking dose-dependent increase in the incidence of hypertension in the 25-100 mg/day dose-range, the 12.5 mg/day dose appears to be safer.