CGA and gastrin-producing neuroendocrine tumor: The baseline serum CgA levels were elevated in 103 of 208 patients (50%) with various NETs, including carcinoid tumors, insulinomas, gastrinomas, non-functioning Pan-NETs, pheochromocytomas, medullary thyroid tumors, neuroblastomas, Merkel cell tumors, and pituitary adenomas [44].