Parathyroid hormone and bone mass after kidney transplantation

Metabolic bone disorder develops during chronic renal failure and chronic dialysis treatment, continues after successful kidney transplantation, and is further aggravated by corticosteroids and immunosuppressants. The recognized risk factors for bone loss, i.e. parathyroid hormone (PTH) secretion, age, duration of hemodialysis, sex and post-transplantation period, were examined in this cross-sectional study of 91 stable kidney transplant recipients. Patient age was 21-67 years, time spent on dialysis 1-216 months, and post-transplantation period 1-228 months. Bone mineral density was measured by dual energy x-ray absorptiometry at the lumbar spine, femoral neck and radius. T-scores (bone mineral density expressed as standard deviation of healthy young population) were used in statistical analyses to avoid sex differences in bone mass. PTH was measured by a commercial kit (9.07 +/- 11.81 pmol/L). The femoral neck and radius correlated negatively with PTH and hemodialysis duration both in simple correlations and multiple regression, and femoral neck additionally with age. The lumbar spine correlated negatively only with PTH. Post-transplantation time did not correlate significantly with the three densitometry sites. Also, the frequency of osteoporosis or osteopenia for the femoral neck and spine did not differ between the first 12 months and subsequent period, but was positively influenced by hemodialysis duration. There was no sex difference for the variables analyzed in the study. The results indicated that prolonged hemodialysis treatment and consequently increased PTH secretion had unfavourable effect on the femoral neck and radius bone in kidney transplant recipients. Regarding predictors in this study, only PTH was found to adversely affect the lumbar spine. Further deterioration of change in the skeletal status could not be demonstrated, which might be explained by the reduction in PTH secretion and possibly by improvement of the bone disorder.