Effectiveness of low dose cyproterone acetate compared to standard dose in feminizing hormone treatment: a single institutional retrospective pilot study

Abstract

Background: Data regarding the effectiveness of low-dose cyproterone acetate (CPA) in testosterone suppression as feminizing hormone therapy (FHT) in individuals assigned male at birth (AMAB) are sparse. Aim: To assess the effectiveness in testosterone suppression using low-dose CPA (<25 mg/day) compared to standard-dose CPA (25-50 mg/day) in FHT. Methods: A retrospective cohort study of 59 individuals AMAB using CPA was done at a tertiary care center in Bangkok, Thailand between January 2014 and July 2022. Outcomes: The main outcomes included a median time when the testosterone was suppressed (<50 ng/dL), the proportion of individuals AMAB who achieved the targeted testosterone level at 3 months, and the testosterone level at each follow-up. Changes in clinical data were assessed. Results: Among 59 individuals AMAB, 37 initiated CPA with available testosterone levels at the 3-month follow-up. Twenty-two individuals AMAB started with low-dose CPA (12.5 mg/day), and 15 individuals AMAB started with standard-dose CPA. The median time to reach targeted testosterone was 3 months in both groups (adjusted hazard ratio 0.60, P =. 489). At 3 months, 72.7% of those on low-dose CPA and 86.7% of those on standard-dose CPA achieved targeted testosterone (adjusted relative risk 0.85, P =. 606). Testosterone levels at all follow-up visits were not significantly different. The standard dose group had higher high-density lipoprotein cholesterol (HDL-C) but lower low-density lipoprotein cholesterol (LDL-C) and alanine aminotransferase (ALT). Clinical Translation: This study supports a paradigm shift toward using lower-dose CPA in FHT. Strengths and Limitations: This is one of a few studies showing the effectiveness of low-dose CPA in testosterone suppression within 3 months. Limitations include a small sample size and missing data. Conclusions: Testosterone suppression is comparable between CPA 12.5 mg/day and the standard dose in FHT.