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Progesterone in feminizing gender affirming hormone therapy: study protocol for a randomized placebo-controlled trial
David R Cromer1, Daniela S Diego2, Thomas Luke3
1Division of Endocrinology, Metabolism, and Lipids, Department of Medicine, Emory University, Atlanta, United States.
Background:
Transgender women receiving feminizing hormone therapy increasingly request progesterone based on anecdotal reports of improved breast development, sleep, mood, and quality of life. However, evidence supporting progesterone as an adjunct to feminizing gender-affirming hormone therapy remains limited.
Methods:
This randomized, double-blind, placebo-controlled clinical trial will evaluate oral micronized progesterone 200 mg nightly versus matched placebo in transgender women aged 18-60 years who have been receiving stable feminizing hormone therapy for at least 6 months. Participants will be followed monthly for 6 months. Baseline assessments include blood pressure, height, weight, breast hemi-circumference, and validated questionnaires assessing psychological distress, sleep quality, and gender congruence/life satisfaction: the Kessler Psychological Distress Scale, Pittsburgh Sleep Quality Index, and Gender Congruence and Life Satisfaction Scale. Monthly visits will assess medication adherence, side effects, and adverse events. Questionnaires will be repeated at month 3 and month 6. The final visit will include repeat physical measurements, breast hemi-circumference, questionnaires, laboratory testing, and return of remaining study medication. The primary outcome is change in psychological distress at 6 months. Secondary outcomes include changes in sleep quality, gender congruence/life satisfaction, breast hemi-circumference, blood pressure, lipid measures, estradiol, creatinine, alanine aminotransferase, and aspartate aminotransferase. Adverse events will be summarized by treatment group.
Discussion:
This study will evaluate the role of oral micronized progesterone as an adjunct to standard feminizing hormone therapy. It is designed to assess physical and cardiometabolic outcomes, as well as adverse events, to inform the safety, feasibility, and potential clinical role of progesterone in transfeminine care.
Trial Registration:
Registered in www.clinicaltrials.gov on January 29, 2025 with registration number NCT06807580. FDA IND #171225.
