Gender-Affirming Hormone Therapy and Bone Health: Do Different Regimens Influence Outcomes in Transgender Adults? A Narrative Review and Call for Future Studies.

BACKGROUND: Gender-affirming hormone therapy (GAHT) influences bone health in transgender individuals. Several hormone preparations and administration routes are available for GAHT, but no studies have compared clinical and laboratory bone health measures across different GAHT regimens. CONTENT: We searched PubMed (MEDLINE), Embase, and Google Scholar for studies measuring bone turnover markers and bone mineral density before and during GAHT in transgender adults. We summarized bone health data by hormone type and administration route (estrogen or testosterone; oral, transdermal/percutaneous, intramuscular). Among trans women, we also examined outcomes among regimens containing different adjunctive agents (antiandrogens or gonadotropin-releasing hormone analogs). SUMMARY: Most hormone preparations maintained or increased areal bone mineral density among trans adults taking GAHT for at least 12 months from baseline. Different bone turnover markers were measured across studies, and we were unable to compare or comment on the direct influence of selected hormone preparations on these clinical laboratory measures. Larger and uniformed studies are needed to measure volumetric bone mineral density and biomarkers of bone metabolism in trans adults taking standardized GAHT regimens.