Serum concentrations of vitamin D and parathyroid hormone and prevalent metabolic syndrome among adults in the United States

Abstract

Some reports suggest that concentrations of vitamin D are inversely, whereas concentrations of parathyroid hormone (PTH) are directly, associated with prevalent metabolic syndrome. Because of lingering uncertainty about these associations, we examined the cross-sectional associations between serum concentrations of 25-hydroxyvitamin D(3) and PTH with metabolic syndrome in a representative sample of adults in the US. We used data from 1705 participants in the 2005-2006 National Health and Nutrition Examination Survey. Vitamin D was measured by radioimmunoassay, whereas PTH was measured using an electrochemiluminescent process. The mean concentration of vitamin D for participants with and without metabolic syndrome was 20.3 and 22.9 ng/mL, respectively (P = 0.001). The mean concentration of PTH for participants with and without metabolic syndrome was 44.5 and 41.0 pg/mL, respectively (P = 0.002). The age-adjusted mean concentrations of vitamin D (P for linear trend <0.001) decreased linearly, whereas PTH (P for linear trend = 0.002) increased linearly, as the number of components of metabolic syndrome increased. After adjusting for age, gender, physical activity, urinary albumin creatinine ratio, and concentrations of C-reactive protein and calcium, concentrations in the highest quintile of vitamin D [prevalence ratio (PR) = 0.59; 95% confidence interval (CI) 0.44-0.79], but not PTH (PR = 1.18; 95% CI 0.97-1.43), was significantly associated with prevalent metabolic syndrome. Concentrations of vitamin D, but not PTH, were significantly associated with prevalent metabolic syndrome among US adults.