Dahlgren et al. [13] suggested that the increased risk of T2DM in T allele carriers is associated with dysfunction in the production of insulin within the beta cells and Lyssenko et al. [14] showed that the presence of the T allele results in overexpression of TCF7L2 in the pancreatic β cell, with a reduced insulin secretion in turn increasing hepatic glucose production. The gene discussed is TCF7L2; the disease is type 2 diabetes mellitus.