The relationship between serum 25-hydroxy vitamin D concentration and obesity in type 2 diabetic patients and healthy subjects

Background: Both obesity and type 2 diabetes are associated with hypovitaminosis D. The aims of this study were to investigate the association of serum 25-hydroxy vitamin D (25(OH) D) and parathyroid hormone (PTH) concentration with body mass index (BMI) in type 2 diabetic patients compared to control subjects and their predicting role in obesity. Methods: This cross-sectional study was conducted on 200 subjects (100 type 2 diabetics and 100 healthy controls). Concentration of 25(OH) D, calcium, phosphorous, parathyroid hormone (PTH), fasting blood glucose, HbA1c, serum insulin, homeostasis model assessment of insulin resistance (HOMA-IR) was determined in the fasting samples. Anthropometric measurements including body mass index (BMI) were also measured. Results: Eighty-five percent of type 2 diabetics and 79% of healthy subjects were suffering from vitamin D deficiency or insufficiency. Serum concentration of 25(OH) D (22.08 +/- 15.20 ng/ml) (r = -0.11, P = 0.04) and calcium (8.94 +/- 0.59 mg/dl) (r = -2.25, P = 0.04) has significant statistically with BMI in type 2 diabetic patients. Serum concentration of PTH has non-significantly associated with BMI in diabetic patients and healthy subjects. Conclusion: Serum levels of vitamin D inversely and PTH positively are associated with BMI after adjusted for age, gender and serum calcium in both type 2 diabetic patients and healthy subjects. These associations were statistically significant for serum concentration of vitamin D and calcium only in diabetic patients. So the status of vitamin D is considered as an important factor in type 2 diabetic patients.