Association of sex hormone status with the bone loss of renal transplant patients

Background. Bone loss is an important problem in renal transplantation recipients. The role of sex hormones in this setting has not been previously addresssed. The objective was to investigate whether sex hormone status is associated with bone mass loss in renal transplant recipients. Methods. Thirty patients (16 men and 14 women, of which eight were post-menopausal) were studied by bone densitometry and bone biopsy. In women, serum oestradiol levels and menopausal status were determined: in men, serum testosterone levels were assessed. Results. Mean age was 48±11 years. Time on dialysis was 13±17 months, and time since transplantation was 125±67 months. Thirteen patients were on cyclosporine A (CsA) monotherapy, 12 on azathioprine plus prednisolone (PRED) dual therapy, and five on CsA, azathioprine and PRED triple therapy. In men, serum testosterone levels were 19.7±6.8 nmol/l (mean± SD). In pre-menopausal women, oestradiol serum levels were 209(128-289) pmol/l (median (percentiles 25-75%)), and in post-menopausal women 93(54-299) pmol/l (non-significant). Univariate analysis in women demonstrated that serum oestradiol levels were positively correlated with Z scores of osteoblast surface (r=0.70, P=0.005), osteoid surface (r=0.75, P=0.002) and trabecular wall thickness (r=0.68, P=0.008). In men, a weak correlation was seen between serum testosterone levels and the cumulative dose of PRED (r=0.52, P=0.06). In the multivariate analysis, two models of multiple regression were employed (one for women and one for men), considering the densitometric and histomorphometric variables (Z scores) as dependent variables. Serum testosterone in men did not predict any of the densitometric nor histomorphometric variables analysed, while serum oestradiol in women was an independent predictor for the osteoblast surface (r=0.81, P=0.003), osteoid surface (r=0.82, P=0.009) and trabecular wall thickness (r=0.54, P=0.05). Conclusion. In female renal transplant recipients, serum oestradiol levels independently predict the bone status, while in men, factors other than testosterone seem to influence bone loss. Our results give rise to the hypothesis that sex hormone replacement therapy may play a role in prevention and/or treatment of the bone loss in women following renal transplantation