The metabolic syndrome and carotid intima-media thickness in relation to the parathyroid hormone to 25-OH-D3 ratio in a general population

Abstract

Objective: Parathyroid hormone (PTH) and vitamin D interactively regulate calcium fluxes across membranes, and thereby modulate insulin sensitivity, blood pressure and arterial calcification. We hypothesized that lower calcium intake as reflected by circulating PTH and 25-OH-D3 might be associated with the metabolic syndrome (MS) and arterial calcification. Design and method: In a random population sample (n = 542; 50.5% women; mean age, 49.8 13.1 years), we measured MS prevalence (IDF and AHA criteria), PTH and 25-OH-D3, serum and 24-h urinary calcium, MS components, carotid intima-media thickness (CIMT) and calcium intake from dairy products. We assessed associations in multivariable-adjusted analyses, using linear and logistic regressions. Results: The prevalence of MS was 21.0% (IDF criteria) and 23.6% (AHA criteria). MS prevalence, blood pressure, waist circumference, body mass index, fasting blood glucose, insulin and triglycerides, and CIMT increased (P<0.042) across quartiles of the PTH/25-OH-D3 ratio, whereas serum and 24-h urinary calcium decreased (P<0.029). Waist circumference and fasting blood glucose decreased across quartiles of habitual calcium intake (P<0.04). In models that included MS (IDF) and PTH/25-OH-D3, the regression coefficients for PTH/25-OH-D3 ratio and MS were +51.3-m (P = 0.013) and +18.9-m (P = 0.45), respectively. Multivariable adjusted analyses were confirmatory. Conclusions: MS prevalence and CIMT were positively associated with PTH/25-OH-D3. CIMT was not associated with MS In the presence of PTH/25-OH-D3. Assuming causal and reversible associations, a high dietary calcium intake might protect against arterial calcification and MS.