A number of clinical research studies has been performed since the first study on two patients with insulinoma using [Lys40(Ahx-DTPA-111In)NH2]-exendin-4 (DTPA: diethylenetriamine tetraacetic acid) for the imaging of GLP-1R 64 and nowadays several multicenter clinical trials using various GLP-1 analogues are ongoing in Europe 26, 37, 64-66, 147-149. This evidence concerns the gene GLP1R and pancreatic insulinoma.