Hypovitaminosis D in chronic kidney disease.

BACKGROUND AND OBJECTIVES: Recent studies show high prevalence of suboptimal 25-hydroxyvitamin D levels in chronic kidney disease patients. This study sought to test the hypothesis that the prevalence of 25-hydroxyvitamin D deficiency is significantly higher in chronic kidney disease patients and, in diabetic nephropathy, low serum 25-hydroxyvitamin D is associated with abnormal serum parathyroid hormone, bone mineral density, and coronary artery calcification. DESIGN, SETTING, PARTICIPANTS, & MEASUREMENTS: Study A used data from the Third National Health and Nutrition Examination Survey. Study B was a post hoc analysis of an observational study of coronary artery calcification in non-dialysis-dependent diabetic nephropathy.
RESULTS: In study A, the adjusted odds for 25-hydroxyvitamin D deficiency were 32% higher in chronic kidney disease patients. This higher prevalence of 25-hydroxyvitamin D deficiency, however, could not be explained by differences in total vitamin D intakes. The consequences of suboptimal 25-hydroxyvitamin D levels were analyzed in 146 patients with diabetic nephropathy. The significant, inverse relationship between serum 25-hydroxyvitamin D and parathyroid hormone levels was attenuated to a nonsignificant level on multivariate adjustment. There was a significant, inverse relationship between bone mineral density and coronary artery calcification scores; neither was independently associated with serum 25-hydroxyvitamin D. The serum 25-hydroxyvitamin D levels declined modestly in 72 patients studied after 12.4 +/- 0.4 mo.
CONCLUSIONS: 25-Hydroxyvitamin D deficiency is more common in chronic kidney disease, but this higher prevalence is unlikely to be a result of lower vitamin D intakes. The consequences of suboptimal 25-hydroxyvitamin D levels remain to be definitively elucidated.