Short-Term Changes in Bone Metabolism Among Transgender Men Starting Gender-Affirming Hormone Therapy: A Systematic Review and Meta-analysis

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Transgender and gender diverse individuals experience a gender identity that differs from the sex assigned at birth. Some transgender men may request testosterone to induce virilization; however, its impact on bone health remains to be fully elucidated. The objective of this systematic review and meta-analysis was to evaluate the modifications in bone metabolism over a short-term period among transgender men initiating testosterone therapy. A systematic search was conducted in PubMed, Scopus, Web of Science, and Cochrane Library. The articles of interest had to report longitudinal evaluation conducted among transgender men, before starting testosterone and after 12 and 24 months of therapy. The analyzed parameters were BMD, calcium, phosphate, 25OHD, PTH, P1NP, BAP, osteocalcin and CTx. Mean differences with 95% coefficient intervals were combined using random effects models. Funnel plot, Egger’s test, and trim-and-fill analysis were used to assess publication bias. Fourteen studies met the inclusion criteria, including 1484 subjects. In absence of heterogeneity, BMD did not significantly change at lumbar spine, hip, femoral neck, and whole-body evaluations. Calcium, phosphate, 25OHD and PTH remained stable over time. Regarding bone turnover markers, only P1NP showed a statistically significant increase after 12 months of T therapy, in absence of heterogeneity (SMD 0.61 mcg/l; 95% CI: 0.40–0.83; p < 0.0001; I2 = 0%, Pforheterogeneity = 0.48). Testosterone therapy among transgender men seems not to disrupt bone health after 12 and 24 months. A statistically significant elevation in P1NP levels after 12 months of therapy may indicate a positive anabolic effect of testosterone in the short-term.