Starting gonadotropin-releasing hormone agonist (GnRHa) treatment in early puberty followed by use of gender-affirming hormones (GAH) can alter bone geometry to match that of the experienced gender for transgender individuals, according to the results of a study published in the Journal of Bone and Mineral Research.

Although adult transgender individuals experience no change in bone geometry during GAH treatment, the impact of GAH on the bone geometry of transgender individuals who start this treatment during puberty has not been established, according to van der Loos et al. This study was designed to investigate changes in bone geometry among transgender adolescents who used GnRHa and GAH before achieving peak bone mass.

The researchers examined retrospective data from 332 adolescents (31.9% trans women) treated with GnRHa and subsequent GAH before the age of 18 were included. Participants were categorized by their Tanner stage at the start of GnRHa treatment into early, mid, and late puberty groups. Hip structure was measured using dual-energy X-ray absorptiometry (DXA) scans at the start of GnRHa and GAH treatments and after 2 or more years of GAH treatment.


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For individuals who started GnRHa during early puberty, their bones resembled the reference curve for the subperiosteal width (SPW) and endocortical diameter (ED) of their experienced gender. Individuals who started GnRHa in mid or late puberty did not experience this change and more closely resembled the bone geometry of the gender assigned at birth.

The findings suggest that “the main effect of testosterone and estrogen on periosteal and endocortical bone growth occurs during early puberty,” the study authors wrote. 

Study limitations include the lack of reference data for HSA parameters, the use of DXA devices from varying manufacturers, the use of DXA for bone geometry measurements, and the small sample size of trans men. The researchers called for future studies that correct for these limitations.

Future research with larger cohorts, consistent DXA machines, and additional bone geometry measures is warranted.

Reference

van der Loos MA, Hellinga I, Vlot MC, Klink DT, der Heijer M, Wiepjes CMet al. Development of hip bone geometry during gender-affirming hormone therapy in transgender adolescents resembles that of the experienced gender when pubertal suspension is started in early puberty. J Bone Miner Res. Published online January 28, 2021. doi:10.1002/jbmr.4262