Tcf7l2 is linked to type-2 diabetes outcome (Grant et al., 2006; Lyssenko et al., 2007; Prokunina-Olsson et al., 2009; Savic et al., 2011) and the strongest risk factor SNPs are located in introns near human tcf7l2 exon 3a (Grant et al., 2006). This evidence concerns the gene TCF7L2 and type 2 diabetes mellitus.