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Disturbances in mineral and vitamin D metabolism, which affect parathyroid hormone (PTH) synthesis, are well recognized in patients receiving dialysis. However, it is unclear at what stage of chronic kidney disease (CKD) these abnormalities develop.The associations between CKD stages 3 and 5, and alterations of calcium, phosphate, vitamin D and PTH concentrations were assessed in 249 patients (mean age 61 years, 66% male) and 79 age- and sex-matched healthy controls.As compared to controls, serum phosphate concentrations were elevated among CKD patients (1.40 vs. 1.11 mmol/l; p < 0.0001). And levels of both 25-hydroxyvitamin D (42.1 vs. 60.4 nmol/l; p < 0.0001) and 1,25-dihydroxyvitamin D (58.2 vs. 119.5 pmol/l; p < 0.0001) were lower among patients with CKD, even among those with only stage 3 CKD and despite 73% of patients receiving vitamin D supplements. The ratio of 1,25-dihydroxy- to 25-hydroxyvitamin D was lower than controls, even among patients with stage 3 CKD (p = 0.0001), and this ratio diminished with advancing renal impairment. Concomitant elevations were observed in intact PTH (13.8 vs. 4.2 pmol/l; p < 0.0001) and whole PTH (7.9 vs. 2.7 pmol/l; p < 0.0001).Impaired conversion of 25-hydroxy- to 1,25-dihydroxyvitamin D is an early feature of renal disease, and progresses as renal function deteriorates.

Original publication

DOI

10.1159/000108652

Type

Journal article

Journal

Nephron. clinical practice

Publication Date

01/2007

Volume

107

Pages

c109 - c116

Addresses

Department of Nephrology, University Hospital Coventry and Warwickshire NHS Trust, Coventry, UK. d.zehnder@warwick.ac.uk

Keywords

Humans, Kidney Failure, Chronic, Vitamin D Deficiency, Hyperparathyroidism, Phosphates, Calcium, Minerals, Parathyroid Hormone, Vitamin D, Renal Dialysis, Cross-Sectional Studies, Homeostasis, Aged, Middle Aged, Female, Male