E-Poster Presentation ESA-SRB-ANZBMS 2021

Bone Microarchitecture in Transgender Adults: a Cross Sectional Study   (#774)

Ingrid Bretherton 1 2 , Shalem Y Leemaqz 3 , Ego Seeman 1 2 , Xiaofang Wang 2 , Ali Ghasem-Zadeh 2 , Thomas McFarlane 2 , Cassandra Spanos 2 , Mathis Grossmann 1 2 , Jeffrey D Zajac 1 2 , Ada S Cheung 1 2
  1. Endocrinology, Austin Hospital , Melbourne, VIC, Australia
  2. Department of Medicine (Austin Health), University of Melbourne, Heidelberg, VIC, Australia
  3. College of Medicine and Public Health, Flinders University , Adelaide, South Australia, Australia

Gender-affirming hormone therapy aligns physical characteristics with an individual’s gender identity, but given estradiol regulates bone remodelling, may compromise bone morphology. We hypothesised that trans men receiving testosterone therapy for masculinisation, due to reduced estradiol concentrations, have compromised bone microarchitecture. In trans women receiving feminising hormone therapy to increase estradiol and lower testosterone concentrations, we hypothesised that bone microarchitecture would be preserved.

 

We compared distal radial and tibial microarchitecture using high-resolution peripheral quantitative CT images in a cross-sectional study of 41 trans men with 71 cisgender female controls, and 40 trans women with 51 cisgender male controls. Differences between groups were expressed as T-scores (standardized deviations (SD) from the mean) and 98% confidence interval given adjustment for multiple comparators.

 

Trans men had higher distal tibial total volumetric bone mineral density (vBMD), 0.71 SD (0.30, 1.12), p<0.01 relative to cisgender female controls with preserved cortical morphology and trabecular bone volume fraction. Trabecular number and separation were similar, but thickness was 0.50 SD higher (-0.08, 0.92), p=0.02 than cisgender female controls. Conversely, trans women had -0.55 SD lower distal tibial total vBMD (-1.01, -0.08), p=0.02 relative to cisgender male controls due to higher cortical porosity, 0.63 SD (0.19, 1.07), p=0.01 and lower trabecular bone volume fraction -0.57 SD (-1.05, -0.08), p=0.02. Trabeculae were fewer -0.47 SD (-0.94, 0.01), p=0.05, thicker 0.49 SD (0.01, 0.96, p = 0.04) but separation was not increased. Distal radius findings were similar.

 

Contrary to the hypotheses, bone microarchitecture was not compromised in trans men, perhaps because aromatisation of administered testosterone prevented bone loss. Trans women may not be protected from microarchitectural deterioration by estradiol administration, perhaps because the dose was insufficient to offset reduced aromatizable testosterone.