Three cases highlighting possible discrepancies in the interpretation of transgender DXA scores

For diagnosis of osteoporosis, a T-score of ≤-2.5 is recommended for all transgender and gender-diverse patients aged 50 years or older, regardless of hormonal status. This case series presents 3 transgender individuals younger than 50 years undergoing gender-affirming hormone therapy (GAHT) who had DXA scores suggestive of osteoporosis. We highlight possible discrepancies in DXA scan interpretations, especially in forearm bone mineral density measurements. We present the baseline (prior to beginning GAHT), 6-month, and 1-year follow-up DXA data along with pertinent labs to include 25-OH vitamin D, calcium, and alkaline phosphatase, for 2 transgender males (assigned female at birth) and 1 transgender female (assigned male at birth) undergoing GAHT who had low Z-scores and T-scores suggestive of osteoporosis. Multiple studies have analyzed the BMD data of individuals taking GAHT over time, which identify possible causes for low baseline Z-scores for transgender females, but less so for transgender males. Other than positional statements, guidelines remain unclear regarding diagnostic approaches to osteoporosis and low Z-scores in transgender individuals who are premenopausal or under 50 years of age. This case series addresses discrepancies in interpretation that may be encountered by clinicians with baseline and follow-up DXAs, especially involving the forearm, during the course of GAHT. This highlights the importance of establishing clearer guidelines for the diagnosis and treatment of osteoporosis and low BMD for chronological age in the transgender population.