GCG and pancreatic insulinoma: Insulinoma (70%) and gastrinoma (20%) are the most frequent functional pNENs, while the remaining so-called rare pNENs include various hormones (5%–10%), such a vasoactive polypeptides (vipoma), glucagon (glucagonoma), serotonin, renin, and GLP1 (glucagon-like peptide 1) (1).