SAT647 Quantifying The Effects Of Gender-Affirming Hormone Therapy On Bone Density Of Transgender Patients: Emerging Results Of A Single-center Study

Disclosure: C.M. Godar: None. S.C. De La Torre: None. O. Bonsu: None. M.K. Shakir: None. T.D. Hoang: None. Introduction: The care of transgender patients with gender-affirming hormone therapy (GAHT) is becoming increasingly common throughout the United States. Estrogen-based hormone therapy has well-known anabolic effects on bone density in post-menopausal women. Few studies have evaluated the long-term effect of exogenous estrogen or testosterone on bone density of transgender patients. Current guidelines do not suggest a recommended age of DXA screening onset or screening interval for transgender patients on GAHT, or whether to use birth gender vs. affirmed gender standards. In this single-center study, we aim to better characterize bone mineral density (BMD) patterns of transgender patients on GAHT over a 1-year period. Methods: 17 transgender patients underwent DXA scan at baseline, 6 months, and 1 year after starting GAHT. 11 transgender females on estradiol and 6 transgender males on testosterone were included. BMD, T-score, and Z-score data for lumbar spine, total hip, femoral neck, and forearm were measured. 2 patients did not receive 6-month scan, but all patients received baseline and 1-year scans. Mean BMD was calculated at all time points. Data were compared to known T-score and Z-score cutoffs for low BMD (T-score: ≥-1 normal, -1.1 to -2.4 osteopenia, ≤-2.5 osteoporosis; Z-score ≤-2 low BMD for age). Results: Mean BMD change for transgender males at 1 year was +1.8% at lumbar spine, -0.7% at femoral neck, +1.4% at total hip, and -13.3% at forearm. Mean BMD change for transgender females was +4.5% at lumbar spine, +2.8% at femoral neck, -6.9% at total hip, and +1.5% at forearm. Using male T-score standards, 1 transgender male who was osteoporotic at baseline was osteopenic at one year. Using female Z-score standards, 1 transgender female with low BMD for age achieved normal BMD at one year. Male Z-score and female T-score trends did not change any individual’s BMD categorization. Conclusion: These results suggest a trend of modest BMD improvement at lumbar spine after patients begin GAHT regardless of gender, with a pattern of worsening total hip BMD in transgender females and worsening forearm BMD in transgender males. These results are limited by a small study population that is growing as data collection continues. Further statistical analyses are needed to determine significance of our findings. Bone density increases may be attributed to hormone therapy, though it is hypothesized that correction of gender dysphoria and greater physical well-being play a role as well. For these variable BMD changes, we suggest that universal DXA screening guidelines could be considered for transgender patients after 1 year of GAHT, though a decision to treat based on abnormal results remains controversial. Studies of longer duration are needed to make conclusions on long-term bone density effects of GAHT. Presentation: Saturday, June 17, 2023