The discovery of the insulinotropic glucose-lowering effects of GLP-1 was a major breakthrough that formed the basis for developing the first generation of synthetic GLP-1 analogues and, subsequently, their approval for the treatment of Type 2 diabetes mellitus (T2DM) and obesity in 2005 [2,3]. The gene discussed is GLP1R; the disease is obesity due to melanocortin 4 receptor deficiency.