GLP1R and pancreatic insulinoma: A number of clinical research studies has been performed since the first publication on 2 patients with insulinoma using [Lys40(Ahx-DTPA-111In)NH2]-exendin-4 for the imaging of GLP-1R [53] and at present several clinical research studies and multicenter clinical trials using various GLP analogs are ongoing in Europe [45,46,53,54,55,64,65,78].