Serum Vitamin D and Parathyroid Hormone in Relation to Cardiac Structure and Function: The ICELAND-MI Substudy of AGES-Reykjavik

Context: Emerging evidence suggests that vitamin D and PTH may play a role in the development of cardiac diseases. Objective: We investigated whether 25-hydroxyvitamin D (25OHD) and PTH concentrations are cross-sectionally associated with cardiac structure and function using magnetic resonance imaging (MRI). Design, Setting, and Participants: ICELAND-MI is a substudy of the Age, Gene/Environment Susceptibility-Reykjavik Study, an older-aged community-dwelling cohort with oversampling of participants with diabetes (29%) and measurements between 2004 and 2007. Serum 25OHD concentrations were measured using an immunoassay (n = 992). Intact PTH concentrations were measured using a 2-site immunoassay (n = 203). We included 969 participants for this cross-sectional analysis (mean age 76 +/- 5.3 years, 51% female). Mean 25OHD was 54.2 +/- 25.5 nmol/L and the median PTH was 4.5 pmol/L (range 1.5-18). Main Outcomes: MRI to measure cardiac structure and function was the main outcome. Results: The lowest 25OHD category (< 25 nmol/L) compared with the highest category (< 75 nmol/L) was associated with a smaller left and right atrial area in unadjusted analyses; however, the associations became nonsignificant after adjustment for covariates. The highest PTH quartile compared with the lowest quartile was significantly associated with a 7.3 g (95% confidence interval 0.8, 13.8) greater left ventricular (LV) mass and a 5.1% (-9.1, -1.1) lower LV ejection fraction compared with the lowest PTH quartile in the fully adjusted model. Conclusions: Serum 25OHD concentrations were not associated with MRI measures in an older white population. Higher PTH concentrations were associated with greater LV mass and lower systolic function and may point to a potential role for PTH as a determinant of cardiac remodeling.