TCF7L2 and type 2 diabetes mellitus: Extensive genome-wide association (GWA) studies revealed that TCF7L2 is a strong candidate for a type 2 diabetes gene, and several studies indicated that the presence of certain common single nucleotide polymorphisms (SNPs) in this gene might increase the incidence of this disease in human [28], [29], [30], [31], [32], [33], [34], [35].