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CONTEXT: Female-to-male transsexual persons (transsexual men) undergo extreme hormonal changes due to ovariectomy and testosterone substitution, allowing studies on sex steroid effects on bone geometry and physiology in the adult. OBJECTIVE: The objective of the study was to examine the effects of cross-gender sex steroid exposure on volumetric bone parameters in transsexual men. DESIGN: This was a cross-sectional study. SETTING: Participants were recruited from the Center for Sexology and Gender Problems at the Ghent University Hospital (Ghent, Belgium). PARTICIPANTS: Fifty transsexual men after sex reassignment surgery with 50 age-matched control women and an additional 16 transsexual men before testosterone substitution and sex reassignment surgery with 16 control women participated in the study. MAIN OUTCOME MEASURES: The main outcome measures were areal and volumetric bone parameters using dual-energy X-ray absorptiometry and peripheral quantitative computed tomography, body composition (dual-energy X-ray absorptiometry), sex steroids, markers of bone turnover and grip strength. RESULTS: Before hormonal treatment, transsexual men had similar body composition and bone geometry as female controls. The transsexual men on long-term testosterone therapy, however, demonstrated a higher lean body mass and muscle mass and a greater grip strength as well as a lower body and subcutaneous fat mass and a larger waist and smaller hip circumference compared with female controls (all P < 0.001). We observed a larger radial cortical bone size (P < 0.001) and lower cortical volumetric bone mineral density at the radius and tibia (P < 0.05) in transsexual men on testosterone therapy. CONCLUSIONS: Transsexual men on testosterone substitution therapy present with a different body composition with more muscle mass and strength and less fat mass as well as an altered bone geometry with larger bones compared with female controls.
Caenegem et al. (Tue,) studied this question.