The first GWAS for T2D, conducted in 2007, with a discovery of about 600 case and control subjects of European ancestry validated the association of TCF7L2 variants to T2D predisposition and identified novel associations with variants at solute carrier family 30 member 8 (SLC30A8) and hematopoietically expressed homeobox (HHEX) [19]. Here, TCF7L2 is linked to type 2 diabetes mellitus.