Patricia Sheean

Background Gender‐affirming hormone therapy (GAHT) is prescribed to produce secondary sex characteristics aligning external anatomy with gender identity to mitigate gender dysphoria. Transgender women are generally treated with oestrogens and anti‐androgens, whereas transgender men are treated with testosterone. The objective of this narrative review was to characterise the influence of GAHT on body composition and bone health in the transgender population to help address weight concerns and chronic disease risk. Methods Studies were extracted from PubMed and Scopus and limited to only those utilising imaging technologies for precise adipose tissue, lean mass, and bone mineral density (BMD) quantification. Results Although methodologies differed across the 20 investigations that qualified for inclusion, clear relationships emerged. Specifically, among transgender women, most studies supported associations between oestrogen therapy and decreases in lean mass and increases in both, fat mass and body mass index (BMI). Within transgender men, all studies reported associations between testosterone therapy and increases in lean mass, and although not as consistent, increases in BMI and decreases in fat mass. No consistent changes in BMD noted for either group. Conclusions Additional research is needed to appropriately assess and evaluate the implications of these body composition changes over time (beyond 1 year) in larger, more diverse groups across all BMI categories. Future studies should also seek to evaluate nutrient intake, energy expenditure and other important lifestyle habits to diminish health disparities within this vulnerable population. Policies are needed to help integrate registered dietitians into the routine care of transgender individuals.