Association between serum vitamin D, parathyroid hormone and metabolic syndrome in middle-aged and older Korean adults

BACKGROUND/OBJECTIVES: This study explored the association between serum 25-hydroxyvitamin D (25(OH)D) or parathyroid hormone (PTH) concentrations and the risk of metabolic syndrome (MetS) in middle-aged and older Korean adults using the most recent, nationally representative survey data. SUBJECTS/METHODS: The study sample consisted of 2624 Korean adults (>= 50 years old) who participated in the fifth Korean National Health and Nutrition Examination Surveys. Serum 25(OH)D was measured by radioimmunoassay and serum PTH was measured using chemiluminescence assay. MetS was defined according to the joint interim statement of the International Diabetes Federation and the American Heart Association/National Heart, Lung, and Blood Institute. RESULTS: Serum 25(OH)D concentrations were significantly lower in subjects with MetS than in subjects without MetS, and the prevalence of MetS significantly decreased according to quartiles of serum 25(OH)D concentration. Serum 25(OH)D concentrations were negatively associated with the risk of elevated blood pressure (P for trend = 0.039), hypertriglyceridemia (P for trend = 0.0474) and reduced high-density lipoprotein cholesterol (P for trend = 0.0139), whereas serum PTH concentrations were positively associated with the risk of elevated blood pressure (P for trend = 0.0002) after adjusting for age, gender, residential district, education level, income, smoking status, body mass index, alcohol intake and physical activity. Furthermore, serum 25(OH)D concentrations were inversely associated with the risk of MetS after adjusting for confounding factors (P for trend = 0.0163). However, serum PTH concentrations were not associated with the risk of MetS. CONCLUSION: Serum 25(OH)D concentration may be an independent risk factor of MetS among middle-aged and older Korean adults.