Safety of gender affirming treatment in assigned female at birth transgender people and association of androgen and estrogen β receptor polymorphisms with clinical outcomes

Purpose Gender affirming hormone treatment (GAHT) with androgens in assigned female at birth (AFAB) people with Gender Incongruence (GI) can induce and maintain variable phenotypical changes, but individual response may be genetically determined. To clarify the role of AR and ERβ polymorphisms we prospectively evaluated AFAB subjects undergoing virilizing GAHT. Methods Fifty-two AFAB people with confirmed GI were evaluated before (T0) and after 6 (T6) and 12 months (T12) of testosterone enanthate 250 mg i.m. every 28 days. Hormone profile (testosterone, estradiol), biochemical (blood count, glyco-metabolic profile) and clinical parameters (Ferriman-Gallwey score, pelvic organs) were evaluated at each time-point, as well as number of CAG and CA repeats for AR and ERβ, respectively. Results All subjects have successfully achieved testosterone levels within normal male ranges and improved their degree of virilization, in absence of significant side effects. Hemoglobin, hematocrit and red blood cells were significantly increased after treatment, but within normal ranges. Ultrasound monitoring of pelvic organs showed their significant reduction already after 6 months of GATH, in absence of remarkable abnormalities. Furthermore, a lower number of CAG repeats was associated with a higher Ferriman-Gallwey score post treatment and a higher number of CA repeats was associated with uterine volume reduction. Conclusion We confirmed safety and efficacy of testosterone treatment on all measured parameters. This preliminary data hints a future role of genetic polymorphisms to tailor GAHT in GI people, but evaluation on a larger cohort is necessary as the reduced sample size could limit data generalization at this stage.