Sex-hormone-binding globulin is negatively correlated with femoral bone-mineral density in male cardiac-transplant recipients

Osteoporosis and the subsequent increase in incidence of fractures are a common problem after cardiac transplantation. We performed a cross-sectional evaluation of male cardiac-transplant recipients in a late post-transplantation period (4.2 +/- 2.6 years after cardiac transplantation, n = 21). Bone-mineral density was measured by dual-energy X-ray absorptiometry and by quantitative heel ultrasound, and the endocrine characteristics of cardiac-transplant recipients with and without vertebral fractures were investigated. A significant negative correlation was observed between sex-hormone-binding globulin and femoral-neck bone-mineral density (rs = -0.699; p value = 0.001). Linear regression analysis controlling for age and body-mass index proved sex-hormone-binding globulin to be an independent negative predictor for femoral-neck bone-mineral density (r = -0.474; p value = 0.035). Patients with vertebral fractures had significantly lower femoral-neck bone-mineral density (pvalue = 0.035). However, sex-hormone-binding globulin, total and free testosterone, and estradiol did not exhibit significant associations with vertebral fractures in our patients. This investigation demonstrates for the first time an association between high sex-hormone-binding globulin levels and low femoral-neck bone-mineral density in a cohort of male cardiac-transplant recipients. Our data support the important role of sex-hormone-binding globulin in the pathogenesis of post-transplantation bone disease, although--possibly because of the small number of patients--we could not prove an interrelation of sex-hormone-binding globulin with vertebral fractures.