SAT397 A Low Dose Cyproterone Acetate In Feminizing Hormone Treatment

Disclosure: S. Korpaisarn: None. J. Arunakul: None. K. Chaisuksombat: None. T. Rattananukrom: None. Background: A feminizing hormone therapy (FHT) for transgender women (TW) who have not undergone gonadectomy consists of estrogens and antiandrogens. Cyproterone acetate (CPA) is the most common antiandrogen used in Thailand. A standard dose of CPA is 25-50 mg/day. Recent data showed that a low-dose CPA might be effective in testosterone suppression. However, the result was limited due to the small number of subjects. Our recent survey showed that CPA 12.5 mg/day was commonly used among Thai TW. This study aimed to evaluate the effectiveness of CPA 12.5 mg/day in testosterone suppression. Methods: The retrospective cohort chart review was done on all TW receiving FHT in a transgender clinic at Ramathibodi Hospital between January 2014-July 2022. Among the TW who initiated FHT during the study period, the effectiveness and safety of CPA 12.5 mg/day were compared with the standard dose of CPA. Only TW with information at 3-month follow-up were analyzed for a median time of achieving the T level at the goal (<50 ng/dL) using a Cox regression analysis and a proportion of TW achieving T level at goal at 3 months using risk ratio regression model. All TW who initiated CPA were analyzed for changes in laboratory measurements using a generalized estimating equation (GEE). Results: A total of 89 transwomen were initially reviewed. Forty-one TW initiated CPA, and 37 TW had information at the 3-month follow-up visit. Among the latter, 22 TW (59.5%) started with CPA 12.5 mg. The median age of FHT initiation were 19 years (IQR 15-23) in CPA 12.5 mg group and 20 years (IQR 17-27) in the standard CPA dose group (p-value=0.504). Median follow-up time was 7.5 months (IQR 3-12) and 9 months (IQR 6-12), respectively (p-value=0.402). Baseline T levels were not different, with the median level at 518 ng/dL (IQR 173-787) in CPA 12.5 mg and 752 ng/dL (IQR 56-957) in control (p-value =0.653). In terms of effectiveness, the median time when T levels were suppressed at goal (<50 ng/dL) was 3 months in both groups. The proportion of TW who achieved targeted testosterone level within 3 months was 72.7% in CPA 12.5 mg and 86.7% in control with the risk ratio (RR) of 0.84 (95%CI 0.60-1.17, p-value= 0.295) for univariable analysis. The multivariable analysis showed an adjusted RR of 0.85 (95% CI 0.46-1.57, p-value=0.606). The multivariable GEE showed no difference between testosterone level changes. Only the LDL levels was significantly lower in the CPA 12.5 mg dose group with the difference of -13.72 mg/dL (95%CI (-25.86) – (-1.58), p-value=0.027). Other laboratories were not different among the 2 groups. There was no report of cardiovascular disease or new-onset depression in both groups.Conclusion: A CPA of 12.5 mg/day is effective in testosterone suppression as the standard dose of CPA in a FHT for TW with a comparable safety profile. This low-dose CPA regimen could be used as a FHT since it has a 50% cost reduction with equivalent effectiveness. Presentation: Saturday, June 17, 2023