Sublingual Estradiol Offers No Apparent Advantage Over Combined Oral Estradiol and Cyproterone Acetate for Gender-Affirming Hormone Therapy of Treatment-Naive Trans Women: Results of a Prospective Pilot Study

Purpose: Chronic gender-affirming hormone therapy (GAHT) with sublingual estradiol (SLE) has not been studied. We aimed to compare GAHT with SLE only, to combined oral (CO) estradiol and cyproterone acetate, in treatment-naive trans women. Methods: Twenty-two trans women enrolled into either the CO arm or the SLE-only arm (0.5 mg four times daily) in this 6-month prospective study. Anthropometric and laboratory variables were collected at baseline and 3 and 6 months. At the study beginning and end, body composition was measured by dual-energy X-ray absorptiometry and bioelectrical impedance, and gender dysphoria, sexual desire, and function were assessed by validated questionnaires. Results: Subjects in the SLE were older, 26.3 – 5.8 years versus 20.1 – 2.3 years, p = 0.006. All anthropometric, body composition, and laboratory variables were identical at baseline. Although dysphoria appeared greater, and sexual function lower at baseline in the CO group, this canceled out after age adjustment. Both treatments induced similar biochemical and hormonal changes. Creatinine, hemoglobin and cholesterol decreased significantly, while testosterone was suppressed to the same level in both groups: 3.22 [1.47–5.0] nmol/L in the SLE group and 2.41 [0.55–8.5] nmol/L in the CO, p = 0.65. Significant changes in body composition toward a more feminine body were noted in both groups. Dysphoria did not significantly improve in either group, while sexual desire and function decreased at six months in both, p < 0.001. Conclusions: Both treatments achieved similar clinical changes. At this stage, SLE, which repeatedly induces alarming excursions of serum estradiol throughout the day, appears to offer no advantage over the CO approach.