Functional pNENs include insulinomas, gastrinomas, glucagonomas, vasoactive intestinal peptide tumors (VIPomas), somatostatinomas, growth hormone-releasing hormone (GHRH)-secreting tumors, and, in very rare cases, tumors that secrete luteinizing hormone, renin, insulin-like growth factor 2, or erythropoietin [38]. This evidence concerns the gene GHRH and gastrin-producing neuroendocrine tumor.