Over one third of long-term renal transplant patients with good graft function had elevated PTH.
Bone mineral density (BMD) may be reduced and parathyroid hormone (PTH) levels elevated in long-term renal transplant patients with good graft function, according to Swedish researchers.
The consequences of this persistent hyperparathyroidism remain unclear. The initial adverse effects of PTH elevations on BMD in renal transplant patients may be offset by the reversal of various uremic metabolic and endocrine disturbances following transplantation, but long-term changes in BMD in such patients are not well known.
In a study, Shahiar Akaberi, MD, and his colleagues at UniversityHospital in Lund collected data on PTH, glomerular filtration rate (GFR), and BMD by dual-energy x-ray absorptiometry (DXA) from 41 renal transplant patients. None of the patients underwent parathyroidectomy or received bisphosphonate treatment during follow-up.
The mean plasma PTH levels obtained from individual patients during the study period ranged from 0.9 to 17.0 pmol/L. Overall, 16 patients (39%) had values above the upper normal limit for plasma PTH (6.9 pmol/L).
The initial DXA was performed at a median of 3.0 years following transplantation and revealed that 41% of the patients had osteopenia and 20% had osteoporosis. Compared with a matched population, the initial DXA showed moderately decreased BMD in the hip and lumbar spine. The follow-up DXA was performed at a minimum of 5 years (median, 6.8 years) after the initial DXA and revealed no overall net changes in BMD in the hip or lumbar spine.
PTH had a significant impact on changes in BMD in the hip, but not the lumbar spine in individual patients, the investigators reported in Transplantation (2006;82:749-752). Patients with normal PTH had no significant changes in hip BMD, whereas hip BMD decreased significantly in those with elevated PTH levels.
The investigators found no linear correlation between mean PTH and GFR. Mean GFR, however, was significantly lower in patients with elevated PTH than in those with normal PTH values (41 vs. 54 mL/min/1.73m2).
A previous study of male renal transplant recipients conducted in the United Kingdom found that osteopenia and osteoporosis are common in these patients, with the hip and radius the most severely affected sites, according to a report in Osteoporosis International (2005;16:142-148). The most important contributing factor, the authors observed, were elevated rates of bone resorption driven by hyperparathyroidism.