Bone Abstracts

Introduction: Pubertal suppression with gonadotrophin releasing hormone (GnRH) analogue is introduced after onset of puberty in adolescents with gender dysphoria (GD). As puberty is a critical period for bone accrual and changes in body composition, alterations in body composition and bone mass may be observed during treatment.

Methods: Thirty-eight adolescents (32/38 assigned females at birth) with GD had dual energy X-ray absorptiometry (DXA) prior to starting GnRH analogue and after one year of therapy. DXA lean mass index (LMI:defined as DXA lean mass/height2) and fat mass index (FMI: defined as DXA fat mass/height²) were converted to Z-scores based on LMI and FMI centiles from a cohort of healthy children from Glasgow. DXA total body less head bone mineral content (TBLH-BMC) and DXA lumbar spine bone mineral apparent density (LS-BMAD) were converted to Z-scores based on UK normative data. TBLH-BMC was adjusted for lean mass, fat mass, height, age and ethnic background.

Results: Median age at baseline was 14.2 years (10.6,15.7) with 33/38 (87%) in late puberty (Tanner IV and V). Median body mass index (BMI) Z-score, at baseline and after one year of treatment, was +0.9(−1.7,+3.4) and +1.4(−0.8,+3.5), respectively [P<0.0001]. Median FMI Z-score, at baseline and at one year, was +0.8(−1.1,+2.1) and +1.0(−0.1,+3.2), respectively [P<0.0001]. Median LMI Z-score was −0.6(−2.8,+2.6) at baseline, and −0.7(−3.6,+1.5) at follow-up [P<0.0001]. Twelve months of pubertal suppression led to reduction of LS-BMAD Z-score, from median of −0.1(−2.2,+2.3) at baseline to median of −0.5(−2.7,+1.8) at 1 year [P<0.0001]. Similarly, median TBLH-BMC Z-score was +0.4(−2.6,+3.6) at baseline, and +0.2(−2.8,+2.9) at follow-up, [P=0.03]. LS-BMAD Z-score was positively associated with baseline LMI Z-score [r=0.43, P=0.007] and follow up ([r=0.47, P=0.003]. In those adolescents (n, 8) who showed a reduction of >1.0 S.D. in LS-BMAD Z-score between baseline and one year, median change in LMI Z-score was −1.1(−1.5,+0.2) compared to median change in LMI Z-score of −0.2(−1.2,+2.7) in those with a reduction of <1.0 S.D. in LS-BMAD Z-score between [P=0.003].

Conclusion: Adolescents with GD have relatively low lean mass and relatively high fat mass at baseline. After one year of treatment with GnRH analogue, they showed further reduction in lean mass, an increase in fat mass and a reduction in bone density, at both lumbar spine and total body.

Disclosure: The authors declared no competing interests.