BONE-MINERAL DENSITY AFTER KIDNEY-TRANSPLANTATION - A CROSS-SECTIONAL, STUDY IN 190 GRAFT RECIPIENTS UP TO 20 YEARS AFTER TRANSPLANTATION

Kidney transplant recipients are exposed to multiple factors that lead to osteoporosis after kidney transplantation. Recent short-term longi tudinal studies revealed a strong decline of bone mineral density (BMD ) within 1 year after transplantation. The long-term course of BMD aft er transplantation is still unknown, Therefore, we performed a cross-s ectional study to determine BMD in 190 renal graft recipients (mean ag e 44 years, range 20-71 years) by dual-energy x-ray absorptiometry at various time intervals up to 20 years after transplantation (range 0-2 37 months). Mean BMD of graft recipients was lower than BMD values of an age- and sex-matched European reference collective at every time of measurement after renal transplantation (P<0.01). Lowest mean BMD val ues were measured 12-24 months after transplantation. No loss of BMD o ccurred after the second posttransplant year beyond the normal age and sex-dependent decline of BMD. Mean daily prednisone dosage was signif icantly higher within the first 2 posttransplant years compared with t he later posttransplant period (13.1+/-6.2 vs. 6.7+/-3.4 mg/day). Othe r drugs or metabolic causes, including daily dosage of CsA, AZA, parat hormone level, and graft function, did not show additional important d ifferences before and after the second posttransplant year. Interpreti ng the results of a cross-sectional study in light of a time-dependent process, we suggest that the preexisting low BMD of kidney transplant recipients at the time of transplantation is further strongly reduced within the initial 2 posttransplant years, probably due mainly to the effect of prednisone therapy. After that time, when prednisone dosage is below a threshold of 7.5 mg/day, only a moderate, normal loss of B MD is apparent, even in patients up to 20 years after transplantation.