Associations of Serum Concentrations of 25-Hydroxyvitamin D and Parathyroid Hormone With Surrogate Markers of Insulin Resistance Among U.S. Adults Without Physician-Diagnosed Diabetes: NHANES, 2003–2006

OBJECTIVE: To examine whether concentrations of serum 25-hydroxyvitamin D (25[OH]D) and parathyroid hormone (PTH) are associated with surrogate markers of insulin resistance (IR) in U.S. adults without physician-diagnosed diabetes. RESEARCH DESIGN AND METHODS: Cross-sectional data (n = 3,206) from the National Health and Nutrition Examination Survey (NHANES) 2003–2006 were analyzed. RESULTS: The age-adjusted prevalence of hyperinsulinemia, high homeostasis model assessment-IR, high GHb, and fasting and 2-h hyperglycemia decreased linearly across quintiles of 25(OH)D but increased linearly across quintiles of PTH (except for a quadratic trend for fasting hyperglycemia). After extensive adjustment for potential confounders, the relationships between 25(OH)D and the markers of IR and 2-h hyperglycemia persisted. Only hyperinsulinemia was positively associated with PTH (P < 0.05). CONCLUSIONS: Among U.S. adults without physician-diagnosed diabetes, low concentrations of serum 25(OH)D were associated with markers of IR. The role of PTH in IR deserves further investigation.