Incidence of breakthrough bleeding in transgender and gender-diverse individuals on long-term testosterone

Little is known about the maintenance of amenorrhea among transgender and gender-diverse individuals with uteri who are using long-term testosterone gender-affirming hormone therapy. Emerging data describe breakthrough bleeding among adolescents on long-term testosterone therapy and among adults who are seeking a gender-affirming hysterectomy. More studies are needed to better understand breakthrough bleeding patterns among transgender and gender-diverse individuals with uteri who are using testosterone, including the frequency, timing, and etiology of bleeding and how these patterns may differ between adults and younger populations.

The primary aim of this study was to characterize the incidence and patterns of breakthrough bleeding in a cohort of transgender and gender-diverse individuals who had been on testosterone for longer than 12 months and who had uteri in situ. Secondary aims included identifying the time to first bleed for those who experienced breakthrough bleeding and the risk factors associated with breakthrough bleeding while on testosterone therapy.

This was an institutional review board-approved, single tertiary center, retrospective chart review of transgender and gender diverse individuals who had been on testosterone for at least 1 year. A primary survival analysis that evaluated the incidence of bleeding was combined with descriptive analyses and an evaluation of the factors associated with bleeding.

Of the 279 patients included in the analysis, the median age of testosterone initiation was 22 years (interquartile range, 19-41), and the median follow-up time was 34 months (range, 12-278). The absolute proportion of individuals who ever experienced breakthrough bleeding on testosterone was 34% (n=96; 95% confidence interval, 29-40). Patients who experienced breakthrough bleeding initiated testosterone at a younger age (20.5 vs 22.0 years; P=.04), had lower mean serum testosterone levels (389.14 vs 512.7 ng/dL; P=.001), were more likely to have a mean testosterone level <320 ng/dL (52% vs 48%; P=.001), and had higher mean estradiol levels (62% vs 49%; P=.003). Survival analyses estimated a breakthrough bleeding incidence rate of 0.09 per year (95% confidence interval, 0.07-1.0). Although 58 people underwent a hysterectomy during the follow-up period, 64% of the cohort who maintained a uterus eventually experienced breakthrough bleeding. The median time to the initial bleeding episode was 22 months (interquartile range, 12-201) after testosterone initiation.

These results suggest that a substantial fraction of transgender and gender-diverse individuals who are using testosterone will experience at least 1 episode of breakthrough bleeding even after their initial year of testosterone use. We recommend that clinicians inform all patients that breakthrough bleeding is a common occurrence even after the first year on testosterone therapy.