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. 2025 Sep 15;232(3):649-658.
doi: 10.1093/infdis/jiaf114.

The Impact of Testosterone Therapy on the Vaginal Microbiota of Transgender Men and Nonbinary People: A Prospective Study

Olivia T Van Gerwen  1 , Kristal J Aaron  1 , Emma Sophia Kay  2 , Krishmita Siwakoti  3 , Angela Pontius  1 , Saralyn Richter  1 , Z Alex Sherman  1 , Keonte J Graves  1 , Ashutosh Tamhane  4   5 , Jacob H Elnaggar  6 , Meng Luo  6 , Evelyn Toh  7 , David E Nelson  7 , Nicholas J Van Wagoner  1 , Christopher M Taylor  6 , Christina A Muzny  1
Affiliations

The Impact of Testosterone Therapy on the Vaginal Microbiota of Transgender Men and Nonbinary People: A Prospective Study

Olivia T Van Gerwen et al. J Infect Dis. .

Abstract

Background: Understanding the impact of testosterone on the vaginal microbiota of transgender men (TGM) and nonbinary people assigned female sex at birth over time is imperative as vaginal dysbiosis and incident bacterial vaginosis (iBV) may cause bothersome genital symptoms and increase human immunodeficiency virus/sexually transmitted infection (HIV/STI) acquisition risk. We investigated shifts in the composition of the vaginal microbiota over time in TGM initiating testosterone for gender-affirming hormone therapy, including development of vaginal dysbiosis and iBV.

Methods: Participants ages ≥18 years, assigned female sex at birth and reporting TGM or nonbinary identity, interested in starting injectable testosterone, demonstrating optimal vaginal microbiota, with no current STI(s) were enrolled. Participants self-collected daily vaginal specimens for 7 days prior to testosterone initiation and 90 days thereafter for vaginal Gram staining and 16S rRNA gene sequencing. Episodes of vaginal dysbiosis and iBV were defined as Nugent scores ≥4 or ≥7, respectively, each for ≥2 consecutive days.

Results: Between February 2022 and November 2023, 9 participants enrolled, 89% (8/9) developed ≥1 episode(s) of vaginal dysbiosis after testosterone initiation, and 56% (5/9) developed iBV. Among those who developed iBV, most did so between days 20 and 40 after testosterone initiation. Community state type (CST) I was found most often in participants who did not develop iBV and CST IV-B most often in participants who developed iBV. Sexual activity and menses also appeared to influence the development of iBV.

Conclusions: The majority of participants developed vaginal dysbiosis including iBV. Additional studies with larger sample sizes are needed to further elucidate how testosterone impacts the vaginal microbiota.

Keywords: bacterial vaginosis; gender-affirming care; sexual health; transgender health; vaginal microbiome.

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Conflict of interest statement

Potential conflict of interest. O. T. V. G. has received research grant support from National Institutes of Health/National Institute of Allergy and Infectious Diseases (NIH/NIAID), Gilead Sciences, Abbott Molecular, and BioNTech; has received consulting fees from Abbott Molecular, GSK, Elsevier, and ThermoFisher; and has served on a scientific advisory board for Scynexis. C. A. M. has received research grant support to her institution from NIH/NIAID, Lupin Pharmaceuticals, Gilead Sciences, Inc, BioNTech, and Abbott Molecular; and reports consulting fees from Abbott, BioNTech, bioMerieux, and Cepheid; honorarium from Abbott, Roche, Elsevier, and the Merck Manuals; and royalties from UpToDate. All other authors report no potential conflicts. All authors have submitted the ICMJE Form for Disclosure of Potential Conflicts of Interest. Conflicts that the editors consider relevant to the content of the manuscript have been disclosed.

References

    1. Herman JL, Flores AR, O’Neill KK. How many adults and youth identify as transgender in the United States?. Los Angeles, CA: Williams Institute of UCLA School of Law, 2022.
    1. Hembree WC, Cohen-Kettenis PT, Gooren L, et al. Endocrine treatment of gender-dysphoric/gender-incongruent persons: an Endocrine Society clinical practice guideline. J Clin Endocrinol Metab 2017; 102:3869–903. - PubMed
    1. Coleman E, Radix A, Bouman W, et al. Standards of care for the health of transgender and gender diverse people, version 8. Int J Transgend Health 2022; 23:S1–259. - PMC - PubMed
    1. Guidelines for the primary and gender-affirming care of transgender and gender nonbinary people. https://transcare.ucsf.edu/guidelines. Accessed 1 December 2024.
    1. James SE HJ, Rankin S, Keisling M, Mottet L, Anafi M. The report of the 2015 transgender survey. Washinton, DC: National Center for Transgender Equality, 2016.