ESPE Abstracts

Context: Transgender adolescents can be treated with puberty suppression (PS) using GnRH agonists (GnRHa), and subsequent hormone therapy (HT). Up to this date, it has not been described at what rate body composition in transgender adolescents changes during the first years of treatment. Also, it is unknown whether Tanner stage at which treatment is initiated, might affect this treatment outcome.

Methods: Transgender adolescents were included in this retrospective study if they were treated with GnRHa prior to HT and had at least one dual-energy X-ray absorptiometry scan during the first three years of PS or HT. Mixed model were used to analyse changes over time in total lean- and fat mass Z-scores using sex assigned at birth as reference. Individuals were divided into early pubertal (Tanner B2-3 or G2-3 at start PS) and late pubertal (Tanner B4-5 or G4-5 at start PS).

Results: In total, 380 trans boys and 168 trans girls were included. In trans boys, lean mass Z-scores decreased by -0.32 (95%CI -0.41;-0.23) and fat mass Z-scores increased by 0.31 (95%CI 0.21;0.41) in the first year of PS and remained stable thereafter. In trans girls, lean mass Z-scores decreased by -1.13 (95%CI -1.29;-0.98) and fat mass Z-scores increased by 1.06 (95%CI 0.90;1.23) over three years of PS. During HT, lean mass Z-scores increased by 0.92 (95%CI 0.81;1.04) and fat mass Z-scores decreased by -0.43 (95%CI -0.57;-0.29) in the first year and remained stable thereafter in trans boys. In trans girls, lean mass Z-scores slightly decreased by -0.19 (95%CI -0.36;-0.03) in the first year and fat mass Z-scores were comparable to start HT after three years (-0.02, 95%CI -0.20;0.16). After three years HT, the lean mass Z-score in trans boys was -0.61 (SE 0.07) and fat mass Z-score was 0.20 (SE 0.10) using male references. In trans girls, lean mass Z-score was 0.18 (SE 0.10) and fat mass Z-score was -0.32 (SE 0.09) using female references. No differences in these Z-scores were observed between early and late pubertal starters.

Conclusions: The decrease in lean mass and the increase in fat mass Z-scores continued throughout 3 years of PS in trans girls whereas these changes were smaller and stabilized after one year in trans boys. A large increase in lean mass Z-scores occurred only during the first year of testosterone treatment. In trans girls, body composition changed only slightly during HT, possibly because most changes had already occurred during PS.