Defining a cutoff point for vitamin D deficiency based on insulin resistance in children.

Background: Vitamin D deficiency is a common worldwide problem. Low levels of serum 25-hydroxy vitamin D [25(OH)D], as a marker of vitamin D deficiency, have been linked to a wide field of health problems, including metabolic diseases such as insulin resistance, type 1 and type 2 DM. There is no universal definition for cutoff value of vitamin D deficiency and it seems that it varies in different populations.

Objective: Most previous studies have used a start rise of PTH as a criteria to detect threshold of serum 25(OH)D, However, the aim of this study was to determine a cutoff point of serum 25(OH)D for vitamin D deficiency based on HOMA-IR.

Materials And Methods: Two hundred and ninety seven healthy children (aged 7-11 years) were enrolled. Serum 25(OH)D and PTH were measured and HOMA-IR was calculated. The ROC curve was utilized to obtain a cutoff of vitamin D deficiency based on HOMA-IR.

Results: 25(OH)D concentrations were inversely correlated with HOMA-IR levels (Spearman's r=-0.14, p=0.016). Serum 25(OH)D cutoff point was 11.6ng/mL (29nmol/L) in relation with HOMA-IR >2.1. By using this cutoff value, the prevalence of vitamin D deficiency was 43.4% in this study population of healthy children.

Conclusion: We found that serum 25(OH)D levels are inversely associated with insulin resistance. These results suggest that in MetS patients it may benefit to determine cutoff value of 25(OH)D levels based on HOMA-IR.