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

Background, Bone loss is an important problem in renal transplantation reci pients. The role of sex hormones in this setting has not been previously ad dressed. The objective was to investigate whether sex hormone status is ass ociated with bone mass loss in renal transplant recipients. Methods. Thirty patients (16 men and 14 women, of which eight were post-men opausal) were studied by bone densitometry and bone biopsy. In women, serum oestradiol levels and menopausal status were determined, in men, serum tes tosterone levels were assessed. Results. Mean age was 48 +/- 11 years. Time on dialysis was 13 +/- 17 month s, and time since transplantation was 125+/-67 months. Thirteen patients we re on cyclosporine A (CsA) monotherapy, 12 on azathioprine plus prednisolon e (PRED) dual therapy, and five on CsA, azathioprine and PRED triple therap y. 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 o estradiol levels were positively correlated with Z scores of osteoblast sur face (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 b etween serum testosterone levels and the cumulative dose of PRED (r=-0.52, P=0.06). In the multivariate analysis, two models of multiple regression we re employed tone for women and one for men), considering the densitometric and histomorphometric variables (Z scores) as dependent variables. Serum te stosterone in men did not predict any of the densitometric nor histomorphom etric variables analysed, while serum oestradiol in women was an independen t 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). Conclusions. In female renal transplant recipients, serum oestradiol levels independently predict the bone status, while in men, factors other than te stosterone seem to influence bone loss. Our results give rise to the hypoth esis that sex hormone replacement therapy may play a role in prevention and /or treatment of the bone loss in women following renal transplantation.