Abstract P060: Serum 25-Hydroxyvitamin D, Parathyroid Hormone and Markers of Glucose Homeostasis in Middle-aged Adults
Background: Epidemiological studies show that blood concentrations of 25-hydroxyvitamin D [25(OH)D] are inversely related to the prevalence of diabetes mellitus, glycemia, and insulin resistance. Low vitamin D levels are also associated with hyperparathyroidism, which itself is risk factor for diabetes and insulin resistance. However, it is unclear whether-or-not vitamin D status is associated with diabetes and insulin resistance independently of parathyroid hormone (PTH) concentrations.
Aims: We tested the hypothesis that serum 25(OH)D and PTH concentrations are associated, independently of each other, with measures of glycaemia, serum insulin, insulin resistance and β-cell function among predominantly non-diabetic adults.
Methods: Participants were a random sample of 2,564 adults aged ≥ 40 years without previous cardiovascular disease from a cross-sectional survey carried out during 1988-90. All participants had a 75 gram 2 hour oGTT. 25(OH)D concentrations were measured by isotope-dilution liquid chromatography-tandem mass spectrophotometry, and serum free insulin and PTH were measured by immunoassay. Insulin resistance was calculated using HOMA-IR equation, and β-cell function with HOMA2-B.
Results: Serum 25(OH)D was negatively correlated with BMI (r=-0.19), HOMA-IR (r=0.15), HOMA2-B (r=-0.12), insulin (r=-0.14), PTH (r=-0.21), fasting glucose (r=-0.11) and 2 hour post Polycose glucose (r=-0.13) with all P<0.001. Partial correlations adjusted for BMI and PTH attenuated the serum 25(OH)D association with HOMA-IR (r=-0.05; P=0.01), HOMA2-B (r=0.01; P=0.53), insulin (r=-0.04; P=0.07), fasting glucose (r=-0.07; P=<0.001) and 2 hour glucose (r=-0.09; P<0.001).
Serum PTH was positively associated with BMI (r=0.12), HOMA-IR (r=0.10), HOMA2-B (r=0.10), and insulin (0.09) with all P<0.001; and with 2 hour glucose (r=0.04; P=0.03), but not fasting glucose (r=0.04; P=0.07). Partial correlations adjusted for BMI and 25(OH)D attenuated the serum PTH associations to the null for HOMA-IR, HOMA2-B, insulin, and 2 hour glucose.
Conclusion: Vitamin D status was inversely associated with degree of glycaemia, and insulin resistance, but not with serum insulin or β-cell function, independently of PTH. PTH was not associated with markers of glycaemia and β-cell function after adjusting for body mass index and 25(OH)D.
- © 2013 by American Heart Association, Inc.