Background <p>Testosterone therapy can also lead to physiologic changes in structures such as the endometrium and ovaries. Given this, testosterone may alter uterine bleeding patterns. Although ultrasounds are routinely performed for the purposes of uterine bleeding on testosterone, there has been little data to support this practice. The goal of this study was to evaluate differences in pelvic ultrasound findings among transgender and gender-diverse individuals on testosterone and determine whether these findings are useful for monitoring abnormal uterine bleeding in this population.</p> Methods <p>This was a retrospective cohort study examining ultrasound findings in transgender and gender-diverse individuals on testosterone who did and did not experience uterine bleeding within 3 months of ultrasound. Demographic and clinical data collected from the EMR included age at testosterone initiation, age at ultrasound, latest body mass index (BMI), latest testosterone and estrogen levels, testosterone dose and route of administration. Additional reproductive history variables included age at menarche, history of menstrual concerns prior to testosterone therapy, and presence of gynecologic comorbidities. Ultrasound findings were reviewed for the indication for imaging, uterine size, endometrial stripe thickness, ovarian size, and any radiology comments regarding the endometrium, uterine body, or ovaries. Chi square analysis was used to test for differences between groups for binary or categorical variables, and one-way analysis of variance (ANOVA) was used to test for differences between groups for continuous variables.</p> Results <p>The final sample included a total of 144 individuals on gender-affirming testosterone, 63 who experienced uterine bleeding within 3 months of ultrasound and 81 who did not experience bleeding. There were no significant difference in endometrial stripe measurements between the two groups (<i>p</i> = 0.901) or in any other measurements taken by ultrasound.</p> Conclusions <p>Our study found no significant differences in pelvic ultrasound findings between transgender and gender-diverse individuals on testosterone with and without uterine bleeding, suggesting that routine ultrasound has limited diagnostic utility in this population. Given the multifactorial nature of bleeding on testosterone, including hormonal and metabolic influences, a trial of medical management may be preferable before imaging in low-risk individuals - particularly given risk that vaginal ultrasounds could exacerbate gender dysphoria.</p>