SAT399 Are Gender-affirming Hormone Therapy Duration And Body Mass Index Associated With Bone Mineral Density In Transgender And Gender Diverse Adults?

Disclosure: S.J. Iwamoto: None. J.D. Rice: None. N.J. Nokoff: None. K.L. Moreau: None. M. Cornier: None. M.E. Wierman: None. M.P. Mancuso: None. M.S. Rothman: None. Background: Sex steroids play crucial roles in bone mineral density (BMD) accrual and maintenance. Data on gender-affirming hormone therapy’s (GAHT) bone effects in transgender and gender diverse (TGD) adults have been limited to non-U.S. cohorts with higher gonadectomy and smoking rates. A higher prevalence of low BMD has been seen in TGD adults prior to initiating feminizing, compared to masculinizing, GAHT (fGAHT, mGAHT). Both fGAHT and mGAHT maintain lumbar spine (LS) BMD and increase Z-scores. Adult femoral neck (FN) and total hip (TH) site data are limited. The associations of GAHT duration and body mass index (BMI) with bone health among U.S. TGD adults are understudied. Objectives: To evaluate the associations between BMDs and Z-scores with GAHT duration and BMI among nonsmoking TGD adults aged 18-40 years, without prior gonadectomy, taking estrogen+spironolactone (fGAHT) or testosterone (mGAHT) for >1 year. Hypotheses: BMDs and Z-scores among fGAHT and mGAHT are within expected male and female reference ranges. Increasing GAHT duration and BMI are each associated with increasing BMDs and Z-scores at FN, TH and LS sites. Methods: Cross-sectional study of FN, TH, and LS bone density outcomes measured by total body dual-energy X-ray absorptiometry (DXA) in 30 adults receiving GAHT within a metropolitan area. Means±standard deviations were calculated. Associations between BMDs and Z-scores and the predictors, GAHT duration and BMI, were estimated for each of the three sites using linear regression. Results: Among fGAHT (n=15, n=0 non-White or Hispanic, age 28.7±4.8 years, GAHT 3.1±2.1 years, estradiol 189.7±119.6 pg/mL, total testosterone 97.6±99.5 ng/dL), mean BMI was in the overweight range (27.6±6.4 kg/m(2)) and mean total body percent fat was 33.7±7.3%. Among mGAHT (n=15, n=3 non-White, n=2 Hispanic, age 28.5±5.7 years, GAHT 4.0±2.0 years, estradiol 46.8±24.0 pg/mL, total testosterone 544.6±332.8 ng/dL), mean BMI was also in the overweight range (BMI 25.3±5.9 kg/m(2)) and mean total body percent fat was 29.8±7.1%. Both fGAHT and mGAHT groups had BMDs and Z-scores within expected male and female reference ranges at all three sites. Increasing BMI among mGAHT, but not fGAHT, was associated with increasing FN and TH, not LS, BMDs and Z-scores using male and female references (p<0.05). GAHT duration was not associated with BMDs or Z-scores. Conclusions: Z-scores in nonsmoking TGD adults taking fGAHT or mGAHT for >1 year, without prior gonadectomy, and with average BMIs in the overweight range, were reassuringly within the expected ranges for age. Increasing BMI, but not GAHT duration, was associated with higher FN and TH, but not LS, BMDs and Z-scores among mGAHT only. Larger studies, especially prospective, are needed to understand the associations between body composition changes (for example, lean mass and fat mass), normal or low BMIs, and gonadectomy with BMDs and Z-scores. Presentation: Saturday, June 17, 2023