Effect of gender affirming hormone therapy on bone mineral density and bone marrow composition in transgender adults

Purpose: The study was aimed at evaluating areal (a) bone mineral density (BMD) and bone marrow adipose tissue (BMAT) in Assigned Male at Birth (AMAB) and Assigned Female at Birth (AFAB) transgender adults before and during gender affirming hormone therapy (GAHT). Methods: The prospective observational pilot study was performed in 23 transgender adults (14 AFAB and 9 AMAB; mean age 24.1 and 27.1 years, respectively]. Testosterone in AFAB and 17-β estradiol, androgen antagonists in AMAB were administered as part of the clinical practice. Lumbar spine (L1-L4), femoral neck, total hip and distal radius aBMD were measured by Dual Energy X-ray Absorptiometry (iDXA, Lunar GE, USA) and BMAT by proton magnetic resonance spectroscopy (1H-MRS) before (T0) and 12 months (T12) after initiating GAHT. L1-L4 trabecular bone score (TBS) was calculated by TBS iNsight (Medimaps, Switzerland). Vertebral fracture assessment was performed by DXA (iDXA, Lunar GE, USA). Results: AMAB had significant reduction in L1-L4 aBMD (p < 0.05) and an increase in TBS (p < 0.05) at T12. All-site aBMD and TBS did not significantly change over time in the AFAB group. No changes in BMAT values were observed in both groups. A negative correlation between BMAT and L1-4 aBMD was observed at T0 (p < 0.05), which remained significant after adjustment for BMI and age. Conclusion: Lumbar spine aBMD declines while TBS increases in AMAB subject during GAHT. BMAT values are not influenced by a 12-month course of GAHT and their association with L1-L4 aBMD are significant before but not during treatment.