Body composition, volumetric and areal bone parameters in male-to-female transsexual persons

Male-to-female (M-->F) transsexual persons undergo extreme changes in gonadal hormone concentrations, both by pharmacological and surgical interventions. Given the importance of sex steroids for developing and maintaining bone mass, bone health is a matter of concern in daily management of these patients.

To provide data on bone metabolism, geometry and volumetric bone mineral density in M-->F transsexual persons.

Twenty-three M-->F transsexual persons, recruited from our gender dysphoria clinic and at least 3 yrs after sex reassignment surgery, together with 46 healthy age- and height-matched control men were included in this cross-sectional study.

Body composition, areal and volumetric bone parameters determined using DXA and peripheral quantitative computed tomography. Hormone levels and markers of bone metabolism assessed using immunoassays. Peak torque of biceps and quadriceps muscles and grip strength assessed using an isokinetic and hand dynamometer, respectively.

M-->F transsexual persons presented lower total and regional muscle mass and lower muscle strength as compared to controls (all P<0.001). In addition, they had higher total and regional fat mass (P<0.010) and a lower level of sports-related activity index (P<0.010). Bone mineral content and areal density (aBMD) of the lumbar spine, total hip and distal radius, as well as trabecular vBMD of the distal radius was lower as compared to controls (P<0.010). At cortical sites, no differences in cortical vBMD were observed, whereas M-->F transsexual persons were characterized by smaller cortical bone size at both the radius and tibia (P<0.010). Lower levels of biochemical markers of bone formation and resorption (P<0.010) suggested decreased bone turnover.

M-->F transsexual persons have less lean mass and muscle strength, and higher fat mass. In addition, they present lower trabecular vBMD and aBMD at the lumbar spine, total hip and distal radius, and smaller cortical bone size as compared to matched controls. Both the lower level of sports-related physical activity as well testosterone deprivation could contribute to these findings. These results indicate that bone health should be a parameter of interest in the long-term follow-up care for M-->F transsexual persons.