Of interest, among the genetic loci tied with type-2 diabetes in humans, the majority relate to the function of the endocrine pancreas while some are linked to increased plasma proinsulin to insulin ratios (e.g., TCF7L2, CDKAL1), indicating that type-2 diabetes develops in individuals genetically predisposed to develop β-cell dysfunction [26,27]. The gene discussed is TCF7L2; the disease is type 2 diabetes mellitus.