There is a growing body of literature on TCF7L2 in the context of glucose homeostasis and diabetes [1–35], with much effort dedicated to elucidating how the SNP alters TCF7L2 expression and how a change in TCF7L2 content in pancreatic islets affects beta cell function [8, 10–16, 19–21, 26–30, 32, 34, 35]. Here, TCF7L2 is linked to diabetes mellitus.