Gender-affirming hormone therapy for transgender men can affect their vaginal microbiome, potentially adversely influencing sexual health outcomes, specifically the occurrence of bacterial vaginosis.

In this prospective longitudinal study, participants who were assigned female sex at birth with natal genitalia and reporting transgender male or nonbinary identity, aged ≥18 years and interested in initiating injectable testosterone were screened. If participants had Amsel criteria and Nugent scoring evaluations consistent with optimal vaginal microbiota, they were enrolled. After enrolment, vaginal samples were tested for Chlamydia trachomatis, Neisseria gonorrhoeae and Trichomonas vaginalis and HIV test results obtained. Overall, nine participants were included in the study, of whom eight identified as transgender men and one as nonbinary.