Secondary Hyperparathyroidism After Kidney Transplantation: A Cross-Sectional Study

Introduction. The purpose of the present study was to investigate the prevalence of hyperparathyroidism among a population of kidney graft recipients. Patients and Methods. We investigated biochemical bone parameters of 509 renal transplant recipients with a mean follow-up of 113 +/- 76 months. Among these patients, 257 patients were treated with either vitamin D or calcium supplements or both. Results. The mean estimated glomerular filtration rate (eGFR) was 47.2 +/- 18.4 mL/min/1.73 m(2) and the mean intact parathyroid hormone (iPTH) level was 144 +/- 149 pg/mL. A total of 70 patients (13.7%) had hypercalcemia defined by a corrected serum calcium >10.2 mg/dL. When the patients were classified according to iPTH concentrations following the Kidney Disease Outcome Quality Initiative (K/DOQI) clinical practice guidelines: 22.4% had iPTH <70 pg/mL; 30.8% between 70 and 110 pg/mL; 16.5% between 110 and 150 pg/mL; 24.3% between 150 and 300 pg/mL; and 6.9% >300 pg/mL. There were no differences in biochemical bone parameters between those that were or were not on calcium and vitamin D supplements, but there was a higher percentage of patients with normal iPTH among the treated group (28.0% vs 16.7%; P = 0.003). In patients not receiving calcium and/or vitamin D supplements, multiple linear regression demonstrated that only time on dialysis, eGFR, and serum 25-hydroxyvitamin D (25OHD) levels were significantly predictive of iPTH concentrations (R(2) = 0.21; P = .000). Conclusions. About 80% of patients displayed high iPTH concentrations. The persistence of hyperparathyroidism was associated with graft dysfunction, longer time on dialysis, and low concentrations of 25OHD. Treatment with vitamin D produced a slight improvement in the prevalence of hyperparathyroidism.