TCF7L2 and type 2 diabetes mellitus: The risk alleles of HNF1A I27L (OR = 1.14, P = 0.04), GCK -30G>A (OR = 1.23, P = 0.01), SLC30A8 R325W (OR = 0.87, P = 0.04), and TCF7L2 rs7903146 (OR = 1.89, P = 4.5 × 10-23) conferred a significantly increased risk of T2D.