Persistent menstruation in transgender people using testosterone gender-affirming hormone therapy

Background: The cessation of menstruation is a common and desired outcome of testosterone gender-affirming hormone therapy (GAHT), for trans and gender diverse (collectively referred to as trans) individuals recorded female at birth. This study aimed to (a) assess the prevalence and characteristics of menstruation before and after commencing testosterone GAHT, and (b) explore factors associated with persistent menstruation. Method: Trans people using testosterone therapy for gender affirmation, aged >= 16 years and living in Australia completed an online cross-sectional survey between 28 August to 31 December 2020. Multivariable logistic regression analysis was applied to estimate the effect size of factors potentially contributing to the cessation or persistence of menstruation 6 months after starting testosterone therapy. Results: There were 401 eligible respondents. Median age for commencement of testosterone GAHT was 23 years (IQR = 20, 28) and the median duration of testosterone therapy was 37 months (IQR = 19, 65). Intramuscular testosterone undecanoate injections were the most used formulation. Persistent menstruation >6 months after commencing testosterone GAHT was reported by 87 (22.8%) participants. The odds of reporting persistent menstruation >6 months after commencing testosterone were (a) higher in people using testosterone gels/creams compared to testosterone injections (OR = 11.3 [1.1, 118.2]), and (b) lower in individuals with a body mass index >= 30 kg/m(2) versus <30 kg/m(2) (OR = 0.5 [0.3, 0.99]). No association was found between persistent menstruation >6 months after commencing testosterone and (a) menstrual regularity prior to commencing testosterone GAHT, and (b) age at commencement of treatment. Conclusion: Persistent menstruation >6 months after commencing testosterone GAHT may be impacted by body mass index and the mode of testosterone administration. This is important information for individuals considering testosterone GAHT as well as for clinicians advising on the benefits and drawbacks of different forms of testosterone administration as well as the likelihood of menstrual cessation.