Most research has investigated vitamin D metabolism in Chinese women with gestational diabetes or with metabolic syndrome [34–36], but one study from Cai et al. found no correlation between 25(OH)D values and insulin resistance [37], though exclusion criteria, such as treatment with insulin and thiazolidinedione administration, were omitted in that cross-sectional study which may have affected the results. This evidence concerns the gene INS and Insulin resistance.