Insights into the Association of Vitamin D Deficiency with Parathyroid Hormone Levels with Relevance to Renal Function and Insulin Resistance

Background: In majority of the studies inverse association between vitamin D and parathyroid hormone levels is documented. Objective: The rationale of the current study was to investigate whether this inverse association is age-dependent and whether it has any role in modulating renal function and insulin resistance. Methods: To test this hypothesis, we have carried out a hospital based study enrolling 848 subjects (558 men and 290 women) with the mean age of 50.9 +/- 15.9 y. Chemiluminometric competitive immune assays were performed using commercial kits to determine 25-OH vitamin D and Parathyroid Hormone (PTH) levels. Fasting glucose levels and serum creatinine were used to evaluate diabetes and renal function. Results: Vitamin D deficiency was predominant irrespective of age group (p = 0.21) and gender (p = 0.12). An inverse association between vitamin D and PTH was observed (r = -0.24) in middle age subjects (p = 0.02). The data segregation based on plasma vitamin D levels which were <20 ng/ml, 20.1-30 ng/ml and >30 ng/ml confirmed the inverse association between vitamin D and PTH levels (p(trend): 0.007). Subjects with low plasma vitamin D and increased PTH exhibited elevated blood urea, serum creatinine and blood glucose. Subjects with 25-OHD deficiency showed a 3.03-folds (95% CI: 2.26-4.07) and 2.09-fold (1.41-3.10) increased risk for diabetes and renal disease, respectively. Conclusion: Based on the results of the present study, it is suggested that those with vitamin D deficiency need to be evaluated for possible presence of renal dysfunction, diabetes/insulin resistance in addition to assessing their PTH status.