Endocrine Abstracts

Background: Cross-sex hormone treatments are used to masculinize or feminize the bodies of female-to-male (FtM) or male-to-female (MtF) transsexuals, respectively. Redistribution of fat mass is expected to occur during the first 1–6 months in transgender males and in the first 3–12 months in transgender females.

Objective: To examine the effects of cross-gender sex hormone therapy (CHT) on body composition in transsexual men and women.

Materials and methods: Observational study. 40 transsexual men and women assisted in the Gender Identity Unit of an endocrinology community from January to September 2017. We measured weight, body mass index(BMI) and body composition by bioelectrical impedance analysis(BIA) at baseline and after mean duration of CHT of 2 years.

Results: We evaluated 40 transsexuals, 19 male-to-female (MtF: 47.5%) and 21 female to male (FtM: 52.5%). Mean age 23.86±11.25 years, mean duration of CHT of 24.7±39.9 months. In MtF(68.8% oral estradiol, 31.2% estradiol transdermal patch,83.3% cyproterone acetate), weight(Kg) and BMI(Kg/m2) increased from 72.12±19.04 to 73.17±19.96 (P<0.03) and from 23.8±5.79 to 24.03±5.85(P=0.04) respectively; difference in body composition by BIA were also observed: fat mass(Kg) from 9.79±7.62 to 12.3±0.43(P=0.03), muscle mass(Kg) 55.45±9.24 to 56.05±8.76 (P=0.015), body water 40.60±6.75 to 41.02±6.42 (P=0.04). FtM (76.9% testosterone cypionate,23.1% testosterone undecanoate) also presented significant difference in body composition:fat mass(Kg) from 18.50±3.55 to 14.14±3.95(P=0.04), muscle mass(Kg) 46.44±2.27 to 49.70±6.55(P=0.026), body water 36.55±5.57 to 33.77±1.84 (P=0.042). No significant difference in weight and BMI were observed.

Conclusion: Oral estradiol is the most frequent estrogen preparation used in transgender woman and testosterone cypionate in transgender men. Testosterone treatment in transgender males resulted in increased muscle mass and decreased fat mass. In transgender females, CHT is associated with change in fat mass redistribution although no difference in weight and BMI were observed.