Sex steroids are important regulators of bone development before puberty and of bone homeostasis throughout adulthood. Gender-affirming therapies with sex steroids are used in transgender and gender diverse persons for treatment of gender dysphoria, which may have profound impacts on their bone metabolism. Many studies have described variable changes in bone density and geometry in transgender cohorts. In order to provide informed guidance on the effect of gender-affirming therapy, the International Society of Clinical Densitometry issued official position statements in 2019 for the performance and interpretation of dual-energy x-ray absorptiometry in transgender and gender-diverse patients. We review the effects of gender-affirming hormone therapy on bone physiology and the changes in bone modulation that have been reported in the literature in transgender patients who have received gender-affirming therapy. We also summarize the recent guidelines for interpretation of dual energy x-ray absorptiometry as an update for the radiologist.