NDT Advance Access originally published online on April 27, 2006
Nephrology Dialysis Transplantation 2006 21(9):2621-2624; doi:10.1093/ndt/gfl201
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© The Author [2006]. Published by Oxford University Press on behalf of ERA-EDTA. All rights reserved. For Permissions, please email: journals.permissions@oxfordjournals.org
Original Articles: Dialysis and Transplantation
Renal function and 25-hydroxyvitamin D concentrations predict parathyroid hormone levels in renal transplant patients
1 School of Medicine and Pharmacology, University of Western Australia, 2 Department of Nephrology, Sir Charles Gairdner Hospital, Perth, WA, Australia, 3 Division of Nephrology, London Health Sciences Center, 4 Department of Medicine, University of Western Ontario and 5 Lawson Health Research Institute, University of Western Ontario, London, Ontario, Canada
Correspondence and offprint requests to: Dr Neil Boudville, School of Medicine and Pharmacology, University of Western Australia, Sir Charles Gairdner Hospital, 4th Floor G Block, Verdun Street, Nedlands, WA 6009, Australia. Email: nboudvil{at}cyllene.uwa.edu.au
Background. Recent guidelines suggest supplementation with ergocalciferol (vitamin D2) in chronic kidney disease stages 3 and 4 patients with elevated parathyroid hormone (PTH) levels and 25-hydroxyvitamin D (25OHD) levels <75 nmol/l. These guidelines are also applied to renal transplant patients. However, the prevalence rates of 25OHD deficiency and its association with PTH levels in renal transplant populations have not been extensively examined. We aimed to document the prevalence rates of 25OHD deficiency [defined by serum levels <40 nmol/l (<16 ng/ml)] and insufficiency [<75 nmol/l (<30 ng/ml)] in a single renal transplant centre, and examine its relationship with PTH levels.
Methods. Serum 25OHD and PTH concentrations were measured in 419 transplant patients attending a single renal transplant clinic over a 4-month period. Demographic and biochemical data were also collected, including serum creatinine, calcium, phosphate and albumin. Simple and multiple linear regression analysis were performed.
Results. In 27.3% of the patients, 25OHD deficiency was present, and 75.5% had insufficiency. On univariate analysis, 25OHD, serum albumin and estimated glomerular filtration rate (eGFR) were significantly associated with PTH levels (P < 0.0001, P = 0.004 and P < 0.0001, respectively). Multiple linear regression demonstrated that only 25OHD, eGFR and serum phosphate were significantly predictive of PTH levels (R2 = 0.19, P < 0.0001). In this model, a 75 nmol/l increase in 25OHD will only result in a maximal reduction in PTH of 2.0 pmol/l.
Conclusions. We conclude that 25OHD deficiency and insufficiency are common in renal transplant patients and may exacerbate secondary hyperparathyroidism. However, 25OHD, eGFR and phosphate only account for 19% of the variability in PTH levels. In addition, even a large increase in serum 25OHD levels is likely to result in only a small reduction in PTH. Therefore, alternative approaches to managing hyperparathyroidism in renal transplant recipients rather than supplementation with ergocalciferol are warranted.
Keywords: cholecalciferol; 25-hydroxyvitamin D; hyperparathyroidism; renal transplant; transplantation; vitamin D
*The authors wish it to be known that, in their opinion, both the authors contributed equally to this work.
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