GCG and neoplasm: Also, for functional NET, which is a hormone-secreting tumor, it is necessary to dosage the non-specific (Chromogranin A, Neuron-Specific Enolase, pancreatic polypeptide, Human Chorionic Gonadotropin and α-fetoprotein) and specific (Serotonin, Gastrin, Insulin, Glucagon, Somatostatin and Vasoactive Intestinal Peptide) neuroendocrine markers, for I-oma being recommended Chromogranin A, Neuron-Specific Enolase and Insulin [49,50,51].