TCF7L2 and type 2 diabetes mellitus: When the TCF7L2 rs290481 TT genotype was used as the reference group, the rs290481 TC and TC/CC genotype were correlated with the increased risk of T2DM [TC vs. TT: adjusted OR = 1.32, 95% CI = 1.03–1.69, P = 0.030 and TC/CC vs. TT: adjusted OR = 1.30, 95% CI = 1.02–1.64, P = 0.032 (Table 3)].