TCF7L2 and type 2 diabetes mellitus: Recent years, some novel loci in genes such as TCF7L2, SLC30A8, HHEX, ETX2, CDKN2A/CDKN2B, IGF2BP2, CDKAL1, FTO, PPARG, and KCNJ11 have been found with susceptibility to T2DM [2,73-76], and these has promoted the development of genetics on T2DM.