Impact of parathyroid hormone on bone density in long-term renal transplant patients with good graft function

Background. It remains unknown whether low-grade hyperparathyroidism persisting beyond the first year postrenal transplantation has any impact on bone density. Methods. Parathyroid hormone (PTH), glomerular filtration rate (GFR), and bone density (by dual-energy x-ray absorptiometry [DXA]) were monitored in the follow-up of our transplant patients. Of 260 long-term renal transplant patients, 41 fulfilled the following criteria: Two DXA measurements performed at least five years apart (median 6.8 years, range 5-9); GFR >= 35 ml/min per 1.73 m(2) body surface area (median 50, range 35-76); no bisphosphonate treatment or parathyroidectomy in the study period. Results. In all, 40% had mean PTH values above the normal limit 6.9 pmol/L (65 pg/ml), and the range was 0.9-17 pmol/L. In the first DXA, 8 of 41 patients had osteoporosis and 17 more had osteopenia. Hip bone density Z-score was -0.60 SD, range (-2.6 to +2.3). The absolute median value (g/cm(2)) remained unchanged until the second DXA, but among patients there was a variation which ranged from -2.3% to + 1.7% per year. In a simple linear regression analysis, these changes were significantly correlated to mean PTH (r(2) = 0.16, P = 0.010). Median lumbar spine bone density was also reduced in the first DXA and was not different at follow-up, but with this variable individual changes did not correlate to mean PTH. Conclusion. Bone density is often reduced and PTH remains elevated in long-term renal transplant patients with good transplant function. Slight to moderate elevation of PTH is associated with reduction in hip bone mineral density.