LACK OF EVIDENCE THAT CYCLOSPORINE TREATMENT IMPAIRS CALCIUM-PHOSPHORUS HOMEOSTASIS AND BONE REMODELING IN NORMOCALCEMIC LONG-TERM RENAL-TRANSPLANT RECIPIENTS

Since the effects of cyclosporine on mineral and bone metabolism are c ontroversial, we studied calcium regulating hormones, calcium phosphor us (Ca-P) metabolism, and bone remodeling, assessed by serum osteocalc in, in long-term renal transplant recipients (RT). Forty-seven normoca lcemic patients with good renal function receiving cyclosporine (CT, n =27) or not (NC, n=20) were studied at baseline and after an oral Ca l oad. CT and NC had similar age, daily dose of steroids, GFR level, and duration of transplantation. Baseline evaluation included 24-hr urina ry Ca, P, TRP, TmP/GrFR, fasting serum intact PTH, 1,25-(OH)(2)D, 25OH D, osteocalcin, Ca, and P. Subjects of the two groups had excessive se cretion of PTH, tubular P wasting, and high serum osteocalcin level, a s is usual in RT. However, there was no difference between CT and NC r egarding any baseline variable. Ten CT and ten NC, matched for duratio n of transplantation and serum PTH level, ingested 1g Ca to achieve an acute dynamic study of PTH secretion and Ca-P metabolism. In both CT and NC, this Ca load caused the same decreases in serum PTH (P<0.001), NcAMP (P<0.05), and urinary P (P<0.001) and the same increases in ser um and urinary Ca (P<0.001), and in both TmP/GFR and TRP (P<0.001). Th ese results strongly suggest that cyclosporine treatment had no signif icant effect on calcium-regulating hormone secretion, P-Ca metabolism, and bone remodeling level. We therefore consider that cyclosporine is unlikely to have any prominent role in the abnormalities of bone endo crine and mineral metabolism that are common in long-term kidney recip ients.