ESPE Abstracts

Context: Skeletal dimensions vary between sexes. Men typically have broader shoulders while women have a wider pelvis. It remains unclear to what extent gender affirming hormone therapy (GAHT) with or without prior puberty suppression (PS) can alter these dimensions in transgender individuals.

Methods: Transgender individuals assigned male at birth (AMAB) and assigned female at birth (AFAB) were included in this retrospective cross-sectional cohort study if they had a dual-energy X-ray absorptiometry (DXA) scan between the age of 18 to 28 years. They were divided into four groups; Early PS (Tanner G or B 2-3) + GAHT, Late PS (Tanner G or B 4-5) + GAHT, GAHT only, and Untreated. Shoulder and pelvis dimensions were measured on DXA scans and compared between groups, with adjustment for height.

Results: Data of 121 individuals AMAB and 122 individuals AFAB was included. Shoulder width was 2.8 cm (95%CI 2.0;3.6) greater in untreated AMAB compared to untreated AFAB. Individuals AMAB in the early PS group, but not in the late PS or GAHT only group, had a smaller shoulder width by 1.3 cm (95%CI -2.1 to -0.5) compared to untreated AMAB. In individuals AMAB in both the early PS and late PS group, pelvic inlet, breadth of the pubic symphysis and interischial distance were greater compared to untreated AMAB resulting in dimensions comparable to untreated AFAB individuals. The largest effects were observed in the early PS group. In individuals AFAB, only the early PS group had a breadth of the pelvic inlet that was smaller by 1.0 cm (95%CI -1.5 to -0.6) compared to untreated AFAB and comparable to untreated AMAB (0.1 cm, 95% -0.3 to 0.6).

Conclusion: Differences in shoulder width towards the affirmed gender were only observed in AMAB individuals who started PS in early puberty. Pelvic dimensions also shift towards the female sizes in individuals AMAB in the late PS group, whereas in individuals AFAB a small shift towards their affirmed gender was observed only in the early PS group. These outcomes suggest skeletal dimensions are only altered by GAHT if endogenous puberty has not yet been completed at start of PS. Future research should focus on possible clinical implications for surgical or obstetrical outcomes in transgender individuals.