General Information About Islet Cell Tumors (Endocrine Pancreas)
Other kinds of lab tests are used to check for the different types of islet cell tumors.
The following tests and procedures may be used:
Fasting serum gastrin test: A test in which a blood sample is checked to measure the amount of gastrin in the blood. This test is done after the patient has had nothing to eat or drink for at least 8 hours. Conditions other than gastrinoma can cause an increase in the amount of gastrin in the blood.
Gastric acid secretion test: A test to measure the amount of acid made by the stomach. A tube is inserted through the nose or throat, into the stomach. Gastrin or insulin is injected into the patient, which causes the stomach to make stomach secretions (gastric acid). Four samples of gastric acid are taken through the tube 15 minutes apart. These four samples are used to find out the lowest and highest amounts of gastric acid made during the test and the pH level of the gastric secretions.
Secretin stimulation test: If the gastric acid secretion test result is not normal, a secretin stimulation test may be done. The tube is moved into the small intestine and samples are taken from the small intestine after a drug called secretin is injected. Secretin causes the small intestine to make acid. When there is a gastrinoma, the secretin causes an increase in how much gastric acid is made and the level of gastrin in the blood.
Calcium infusion test: A test to measure the amount of gastrin in the blood after a drug called calcium gluconate is infused. Blood samples will be taken to measure the amount of gastrin in the blood at set times.
Somatostatin receptor scintigraphy: A type of radionuclide scan that may be used to find small islet cell tumors. A small amount of radioactive octreotide (a hormone that attaches to tumors) is injected into a vein and travels through the blood. The radioactive octreotide attaches to the tumor and a special camera that detects radioactivity is used to show where the tumors are in the body. This procedure is also called octreotide scan and SRS.
Fasting serum glucose and insulin test: A test in which a blood sample is checked to measure the amounts of glucose (sugar) and insulin in the blood. The test is done after the patient has had nothing to eat or drink for at least 8 hours.
C-peptide suppression test: A test in which a blood sample is checked to measure the amount of C-peptide in the blood. Insulin is injected into a vein to lower the patient's blood sugar. This should decrease the amount of insulin and C-peptide that the body releases into the blood. In patients who have insulinoma, the insulin and C-peptide levels do not drop because the tumor is also releasing insulin and C-peptide into the blood.
Venous sampling after arterial stimulation: A procedure used to help find where a tumor has formed in the pancreas. This is done at the same time as an angiogram. Calcium is injected into an artery that goes to one part of the pancreas (the head, body, and tail are tested one at a time). A blood sample is taken from a vein that comes out of the pancreas and is checked for pancreatic hormones. If there is an islet cell tumor in the area of the pancreas that gets blood from the artery that was injected, there will be an increase in the amount of hormone in the blood sample. If the increase is found after injection into the first artery, the tumor is in the area that gets blood from that artery. If there is no increase, another artery is injected and the test continues.
Anti-insulin antibody test: A test in which a blood sample is checked to see if there are antibodies against insulin in it.