Abstract
It is well known that sex steroids, particularly estrogen, play a crucial role in the attainment and maintenance of peak bone density in all people. Transgender (trans) women have been frequently observed to have low bone density prior to initiation of gender-affirming hormone therapy, while trans men generally do not. With pharmacologic estrogen, many studies show improving bone density in trans women. With pharmacologic testosterone, bone density in trans men remains largely unchanged although androgens have indirect effects on bone health via changes in fat and lean mass. Much remains unknown about best practices to optimize bone health, interpret DXA scans and assess fracture risk in trans adults.