The effect of GnRH analogue treatment on bone mineral density in young adolescents with gender dysphoria: findings from a large national cohort

Background: More young people with gender dysphoria (GD) are undergoing hormonal intervention starting with gonadotropin-releasing hormone analogue (GnRHa) treatment. The impact on bone density is not known, with guidelines mentioning that bone mineral density (BMD) should be monitored without suggesting when. This study aimed to examine a cohort of adolescents from a single centre to investigate whether there were any clinically significant changes in BMD and bone mineral apparent density (BMAD) whilst on GnRHa therapy. Methods: A retrospective review of 70 subjects aged 12-14 years, referred to a national centre for the management of GD (2011-2016) who had yearly dual energy X-ray absorptiometry (DXA) scans. BMAD scores were calculated from available data. Two analyses were performed, a complete longitudinal analysis (n=31) where patients had scans over a 2-year treatment period, and a larger cohort over the first treatment year (n=70) to extend the observation of rapid changes in lumbar spine BMD when puberty is blocked. Results: At baseline transboys had lower BMD measures than transgirls. Although there was a significant fall in hip and lumbar spine BMD and lumbar spine BMAD Z-scores, there was no significant change in the absolute values of hip or spine BMD or lumbar spine BMAD after 1 year on GnRHa and a lower fall in BMD/BMAD Z-scores in the longitudinal group in the second year. Conclusions: We suggest that reference ranges may need to be re-defined for this select patient cohort. Long-term BMD recovery studies on sex hormone treatment are needed.