TCF7L2 and type 2 diabetes mellitus: In BMI < 24 kg/m2 subgroup, after adjustment for gender, age, smoking status and alcohol use by logistic regression analysis, the TCF7L2 rs290481 TC/CC and TC genotypes increased the risk of T2DM compared with the TCF7L2 rs290481 TT genotype [TC vs. TT: adjusted OR = 1.50, 95% CI 1.04–2.17, P = 0.031 and TC/CC vs. TT: adjusted OR = 1.49, 95% CI = 1.05–2.12, P = 0.026 (Table 4)].