At the same time, the quality score (TC vs. TT: p = 0.045; TC + CC vs. TT: p = 0.042; C vs. T: p = 0.041) and HWE (CC vs. TT: p = 0.029; CC vs. TC + TT: p = 0.041) were the sources of heterogeneity between the eNOS T786C polymorphism and the risk of T2DM. This evidence concerns the gene NOS3 and type 2 diabetes mellitus.