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Musculoskeletal impact of sex reassignment and testosterone therapy


Transsexual men were assessed for changes in their bone physiology and body morphology before and after sex reassignment surgery, which included ovariectomy and testosterone substitution therapy.

Prior to hormonal treatment, 16 transsexual men showed similar bone geometry and body composition in terms of lean body mass, muscle mass and fat distribution when compared with 16 female controls. A larger group of 50 transsexual men, whose sex reassignment had taken place an average of 8.7 years before and who were receiving ongoing testosterone substitution therapy, were compared with 50 control age-matched women. Their body composition had changed; they showed greater muscle mass and strength and reduced fat mass, as well as significant alterations in bone geometry.

The overall bone mineral content in transsexual men post-sex reassignment was significantly higher than in controls and they had significantly greater bone area at the hip and femoral neck. At cortical sites, such as the proximal radius, transsexual men showed a higher cortical bone area and a greater endosteal (↑6.7%) and periosteal (↑4.5%) diameter, compared with female controls. Their volumetric bone mineral density was also significantly higher at trabecular sites such as the distal radius.

Editor’s comment: These findings might have far-reaching consequences for our understanding of what sex and gender mean for the musculoskeletal system and for body shape. This study also complements recent research showing that testosterone treatment causes a significantly higher increase in gene expression in male osteoclasts compared with female osteoclasts.

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