25-Hydroxyvitamin D Status Based on Estimated Glomerular Filtration Rate in Patients with Chronic Kidney Disease

Abstract

Background/Aims: Accumulating data suggest that vitamin D deficiency is prevalent in patients with chronic kidney disease (CKD). However, comprehensive data are lacking for Koreans. The aim of this study was to survey vitamin D deficiency among patients with CKD in Korea and to identify the relationships among various factors. Methods: We conducted a retrospective cohort study of 444 patients who were divided into four subgroups by estimated glomerular filtration rate (eGFR) for comparisons of mean 25-hydroxyvitamin D [25(OH)D] level and other parameters. In addition, non-dialyzed patients were categorized into four groups based on 25(OH)D levels (<10, 10-19, 20-29, and ≥ 30 ng/mL), and risk factors for severe vitamin D deficiency (<10 ng/mL) were investigated. Results: Of patients with an eGFR ≥ 60 mL/min/1.73 m2, 43% (34/79) showed severe 25(OH)D deficiency, and the mean 25(OH)D level was 11.7±5.3 ng/mL. In CKD3 group, 53.2% (41/77) showed severe 25(OH)D deficiency, with a mean level of 11.3±7.2 ng/mL. In CKD4 group, 53.3% (49/92) had severe 25(OH)D deficiency, with a mean level of 11.0±6.2 ng/mL. Approximately 71% (139/196) of patients in CKD5 group showed severe deficiency, and the mean level was 9.2±5.9 ng/mL. Severe 25(OH)D deficiency was affected by winter season, renal function, diabetes, and low-density lipoprotein cholesterol. The serum parathyroid hormone level was inversely correlated with the 25(OH)D level, such that 25(OH)D < 20 ng/mL were associated with a steep increase in parathyroid hormone. Conclusions: Vitamin D deficiency is highly prevalent in the Korean population. Few patients met a sufficient 25(OH)D concentration, even in the early stages of CKD. Our data suggest that 25(OH)D level of 20 ng/mL is a threshold for a rapid increase in parathyroid hormone levels. (Korean J Med 2012;83:740-751)