RESUMO
OBJECTIVES: Despite regular gender-affirming hormone therapy (GAHT), the presence of uterine bleeding can occur occasionally and cause profound discomfort. This study aimed to evaluate the histologic features and immunohistochemical expression of estrogen (ER), progesterone (PR), and androgen receptors (AR) in the endometrium and myometrium of transgender men receiving testosterone therapy and relate them to clinical and hormonal characteristics. DESIGN: Retrospective cross-sectional study. METHODS: Thirty-four transgender men undergoing gender-affirming surgery were included. Clinical, sociodemographic, and laboratory data as well as anatomopathological and immunohistochemical findings were evaluated. RESULTS: The participants' mean age was 42.35 (SD, 10.00) years, and body mass index was 28.16 (SD, 5.52) kg/m2. The mean GAHT duration before surgery was 5.36 (SD, 3.24) years. The mean testosterone levels were 814.98 (SD, 407.13) ng/dL, and estradiol levels were 55.22 (SD, 25.27) pg/mL. The endometrium was atrophic in 61.8%, proliferative in 17.6%, and secretory in 20.6%. Immunohistochemical receptor analysis revealed that endometrial epithelial cells expressed ER (90%) and PR (80%), with a lower expression of AR (30%). In stromal tissue, the median ER, PR, and AR expression was lower than that in the epithelium (60%, 70%, and 25%, respectively). The myometrium showed high expression of PR (90%) and ER (70%), with the highest expression of AR (65%) being localized to this region. CONCLUSIONS: In the present study, GAHT induced an atrophic condition of the endometrium in two-thirds of the transgender men, with a limited AR expression in the endometrial region. The present results suggest that testosterone-based GAHT for a mean of 5 years is safe in transgender men achieving amenorrhea.