Vitamin D and insulin resistance in postmenopausal Indian women

PURPOSE: The purpose of this study is to investigate the association of the serum 25-hydroxyvitamin D (25-OHD) level with markers of insulin resistance (IR) in postmenopausal Indian women. MATERIALS AND METHODS: This was a cross-sectional study, conducted at a Tertiary Care Hospital in New Delhi, India. Seventy one postmenopausal women (mean age 56.3 ± 7.6 years) were enrolled. Exclusion criteria were known or newly detected diabetics, subjects with chronic renal failure, chronic liver disease or any other chronic inflammatory condition, chronic smokers and chronic alcoholics. Serum calcium (and albumin for calculating corrected calcium), phosphorus, alkaline phosphatase and 25-OHD were measured as parameters of calcium homeostasis. Fasting blood glucose (FBG), systolic and diastolic blood pressures, body mass index (BMI), fasting serum insulin, calculated glucose insulin ratio (GIR), and homeostatic model assessment of insulin resistance (HOMA-IR) were studied as parameters of IR. Data was then analyzed for statistical significance. RESULTS: The mean serum 25-OHD level was 12.73 ± 7.63 ng/ml. The mean BMI was 27.78 ± 5.37 kg/m(2). The mean calculated GIR was 13.14 ± 9.39 and HOMA-IR was 2.31 ± 1.70. Serum 25-OHD was inversely correlated with BMI (correlation coefficient −0.234, P value 0.050) and with HOMA-IR (correlation coefficient −0.237, P value 0.047). However, when 25-OHD was adjusted for BMI the correlation between 25-OHD and HOMA-IR lost its significance. No correlation was found between serum 25-OHD and any other parameters of IR studied. CONCLUSIONS: There is a significant negative linear correlation between 25-OHD and BMI. The significant negative linear correlation between 25-OHD and HOMA-IR was confounded by BMI. There is no correlation between 25-OHD and parameters of IR.