Bone Accrual During Puberty Suppression and Gender-Affirming Therapy in Transgender Adolescents

Importance Puberty is a critical window for bone mass acquisition, determining lifelong fracture risk. Gonadotropin-releasing hormone agonist (GnRHa)–based pubertal suppression followed by gender-affirming hormone therapy (GAHT) is increasingly used in transgender and gender-diverse (TGD) adolescents, raising concerns about peak bone mass. Objectives To quantify changes in bone mineral density (BMD), bone mineral apparent density (BMAD), and z scores in TGD adolescents undergoing GnRHa with or without GAHT, and to identify predictors of skeletal outcomes. Data Sources PubMed, Scopus, Web of Science, and Cochrane Library, from inception through September 2025. Study Selection Longitudinal cohorts assessing BMD, BMAD, or z scores at the lumbar spine, total hip, or femoral neck in TGD adolescents treated with GnRHa with or without GAHT. Ten studies met the inclusion criteria. Data Extraction and Synthesis Data were extracted in duplicate; study quality was assessed using the Newcastle-Ottawa Scale. Random-effects models pooled mean changes across baseline (time 0 [T0]), after GnRHa (T1), and after GAHT (T2), stratified by skeletal site and sex assigned at birth. Metaregressions examined body mass index, age, Tanner stage, and treatment duration. Main Outcomes and Measures Dual-energy x-ray absorptiometry–derived BMD, BMAD, and z scores. Results Ten cohorts comprising 751 adolescents (427 assigned female at birth [AFAB]; 324 assigned male at birth [AMAB]) were included. Lumbar spine z scores declined during GnRHa (AFAB: z -score change, –0.97 [95% CI, –1.09 to –0.85]; AMAB: z -score change, –0.73 [95% CI, –0.93 to –0.53]) despite stable BMD. z Scores used sex-assigned-at-birth normative references. After GAHT, BMD increased (AFAB: BMD mean difference, 0.09 g/cm 2 [95% CI, 0.07-0.10 g/cm 2 ]; AMAB: BMD mean difference, 0.13 g/cm 2 [95% CI, 0.10-0.16 g/cm 2 ]), with partial z- score recovery; values remained below baseline at T2 (AFAB: z -score change, –0.51 [95% CI, –0.69 to –0.34]; AMAB: z -score change, –0.52 [95% CI, –0.82 to –0.21]) but were not consistently statistically different across skeletal sites. Recovery at the total hip and femoral neck was smaller and more heterogeneous. Higher body mass index, shorter GnRHa duration, and longer GAHT exposure were associated with more favorable outcomes. Conclusions and Relevance This systematic review and meta-analysis found that pubertal suppression followed by GAHT was associated with transient z- score reductions and subsequent BMD increases. At T2, z scores remained numerically below baseline but were not consistently statistically different, suggesting an uncertain rather than demonstrated persistent deficit. Timely GAHT initiation is recommended.