Effect of vitamin D supplement therapy on HbA1C and IGF-1 levels in children with type 1 diabetes mellitus and vitamin D deficiency

Background: Studies indicated higher rate of vitamin D deficiency in Iranian children and also its potential role in both pathogenesis and management of Type 1 diabetes mellitus (T1DM), so we aimed to evaluate the impact of vitamin D supplement therapy on glycemic control and level of Insulin-like growth factor-I (IGF-1) in children with T1DM. Methods: In this cross-sectional study, a total of 30 children with T1DM and serum 25-hydroxyvitamin D levels lower than 29 ng/ml were enrolled. In addition to insulin therapy, the patients underwent treatment with 50,000 units of cholecalciferol (vitamin D-3) once a week for a period of 12 weeks. Mean of serum vitamin D, IGF-1 and hemoglobin A(1)C (HbA(1)C), before and after treatment were compared. Results: Serum vitamin D increased significantly after 12 weeks treatment (P<0.001). Mean level of IGF-1 and HbA1c increased and decreased significantly after treatment with vitamin D supplement, respectively (P=0.01 and 0.04). There was a significant negative correlation between HbA1c and IGF-1 (r=-0.69, P<0.001) and 25(OH) D (r=-0.40, P=0.05), 12 weeks after treatment with Vitamin D3 supplement. Conclusion: Our results indicated that vitamin D treatment enhance level IGF-1 which was accompanied by decreased levels of HbA1c in patients with T1DM. So, developing a proper vitamin D treatment guideline specified in T1DM patients would result in better glycemic control and proper prevention of its related microvascular and macrovascular complication.