• Timur Liwinski, Matthias K Auer, Johanna Schröder, Ina Pieknik, Christian Casar, Dorothee Schwinge, Lara Henze, Günter K Stalla, Undine E Lang, Alina von Klitzing, Peer Briken, Thomas Hildebrandt, Jeanne C Desbuleux, Sarah V Biedermann, Paul-Martin Holterhus, Corinna Bang, Christoph Schramm, and Johannes Fuss.
• Clinic for Adult Psychiatry, University Psychiatric Clinics, University of Basel, Wilhelm Klein-Strasse 27, Basel, CH-4002, Switzerland.
• Bmc Med. 2024 Sep 2; 22 (1): 346346.

BackgroundLimited data exists regarding gender-specific microbial alterations during gender-affirming hormonal therapy (GAHT) in transgender individuals. This study aimed to investigate the nuanced impact of sex steroids on gut microbiota taxonomy and function, addressing this gap. We prospectively analyzed gut metagenome changes associated with 12 weeks of GAHT in trans women and trans men, examining both taxonomic and functional shifts.MethodsThirty-six transgender individuals (17 trans women, 19 trans men) provided pre- and post-GAHT stool samples. Shotgun metagenomic sequencing was used to assess the changes in gut microbiota structure and potential function following GAHT.ResultsWhile alpha and beta diversity remained unchanged during transition, specific species, including Parabacteroides goldsteinii and Escherichia coli, exhibited significant abundance shifts aligned with affirmed gender. Overall functional metagenome analysis showed a statistically significant effect of gender and transition (R2 = 4.1%, P = 0.0115), emphasizing transitions aligned with affirmed gender, particularly in fatty acid-related metabolism.ConclusionsThis study provides compelling evidence of distinct taxonomic and functional profiles in the gut microbiota between trans men and women. GAHT induces androgenization in trans men and feminization in trans women, potentially impacting physiological and health-related outcomes.Trial RegistrationClinicaltrials.gov NCT02185274.© 2024. The Author(s).

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