TCF7L2 and type 2 diabetes mellitus: Over the past few decades variants in various candidate genes for T2DM such as KCNJ11 (Gloyn et al. 2003), TCF7L2 (Grant et al. 2006), PPAR-G (Altshuler et al. 2000), CAPN10 (Tsuchiya et al. 2006), GSTT1/M1 (Raza et al. 2014), FTO (Raza et al. 2014), PTPNI (Florez et al. 2005), etc. have been extensively studied and investigated through genetic linkage analysis and association studies to find their possible association with T2DM and declare them as susceptible genes.