Safety and rapid efficacy of guideline-based gender-affirming hormone therapy: an analysis of 388 individuals diagnosed with gender dysphoria

Objective: Hormone treatment is an important part of gender reassignment therapy in gender dysphoria. Previous data about efficacy and safety are commonly based on small cohorts or they comprise former cohorts under meanwhile obsolete therapy regimes. Our objective was to investigate these topics in a large cohort of individuals under guideline-based treatment. Design/methods: Cohort study of medical files of n = 155 male-to-female (transwomen) and n = 233 female-to-male transgender persons (transmen) of an Endocrine outpatient clinic between 2009 and 2017. Results: Median time to reach amenorrhoea in transmen under testosterone monotherapy was 3 months, regardless of whether testosterone undecanoat or gel was used. Transmen with higher levels of hemoglobin 3-4 months after onset of GAHT had a greater chance to reach amenorrhea early, whereas testosterone levels showed no significant correlation (hemoglobin: HR: 1.639; 95% CI: 1.036-2.591, P = 0.035; testosterone: HR: 0.999; 95% CI: 0.998-1.001, P = 0.490). Estradiol levels (rho -0.117; P = 0.316) had no significant influence on breast development in transwomen. Testosterone levels (rho -0.398; P < 0.001) and FAI (rho 0.346; P = 0.004) were significantly negatively correlated with reached Tanner stage. Liver values and blood lipids showed an alignment to reference range of the required sex in both groups. Relevant elevations of liver values were rare (2.44% in transmen, 4.23% in transwomen) and transient in most cases. Most relevant side effects were acne (44.8%), respectively erythrocytosis (up to 5.6%) in transmen and venous thrombembolism (1.9%) in transwomen. Conclusions: Gender-affirming hormone therapy in accordance with current clinical practice guidelines is efficient and safe.