An insulinoma is a tumor in the pancreas that produces too much insulin.
The pancreas is an organ in the abdomen. The pancreas makes several enzymes and hormones, including the hormone insulin. Insulin's job is to reduce the level of sugar (glucose) in the blood by helping sugar move into cells.
Most of the time when your blood sugar level decreases, the pancreas stops making insulin to make sure that your blood sugar stays in the normal range. Tumors of the pancreas that produce too much insulin are called insulinomas. Insulinomas keep making insulin, and can make your blood sugar level too low (hypoglycemia).
A high blood insulin level causes a low blood sugar level (hypoglycemia). Hypoglycemia may be mild, leading to symptoms such as anxiety and hunger. Or it can be severe, leading to seizures, coma, and even death.
Insulinomas are very rare tumors. They usually occur as single, small tumors. But there can also be several small tumors.
Most insulinomas are non-cancerous (benign) tumors. People with certain genetic disorders, such as multiple endocrine neoplasia type I, are at higher risk for insulinomas.
After fasting, your blood may be tested for:
- Blood C-peptide level
- Blood glucose level
- Blood insulin level
- Drugs that cause the pancreas to release insulin
- The response of
your body to a shot of glucagon
CT, MRI, or PET scan of the abdomen may be done to look for a tumor in the pancreas. If a tumor is not seen in the scans, one of the following tests may be performed:
- Endoscopic ultrasound (test that uses a flexible scope and sound waves to view digestive organs)
- Octreotide scan (special test that checks for specific hormone-producing cells in the body)
- Pancreatic arteriography (test that uses special dye to view the arteries in the pancreas)
- Pancreatic venous sampling for insulin (test that helps locate the approximate location of the tumor inside the pancreas)
Surgery is the usual treatment for insulinoma. If there is a single tumor, it will be removed. If there are many tumors, part of the pancreas will need to be removed. At least 15% of the pancreas must be left to produce normal levels of enzymes for digestion.
In rare cases, the entire pancreas is removed if there are many insulinomas or they continue to come back. Removing the entire pancreas leads to diabetes because there is no longer any insulin being produced. Insulin shots (injections) are then required.
If no tumor is found during surgery, or if you can't have surgery, you may get the medicine diazoxide to lower insulin production and prevent hypoglycemia. A water pill (diuretic) is given with this medicine to prevent the body from retaining fluid. Octreotide is another medicine that is used to reduce insulin release in some people.
In most cases, the tumor is non-cancerous (benign), and surgery can cure the disease. But a severe hypoglycemic reaction or the spread of a cancerous tumor to other organs can be life-threatening.
Complications may include:
- Severe hypoglycemic reaction
- Spread of a cancerous tumor (metastasis)
- Diabetes if the entire pancreas is removed (rare), or food not being absorbed if too much of the pancreas is removed
- Inflammation and swelling of the pancreas
Call your health care provider if you develop any symptoms of insulinoma. Seizures and losing consciousness are an emergency. Call 911 or the local emergency number right away.
Insulinoma; Islet cell adenoma, Pancreatic neuroendocrine tumor; Hypoglycemia - insulinoma
Asban A, Patel AJ, Reddy S, Wang T, Balentine CJ, Chen H. Cancer of the endocrine system. In: Niederhuber JE, Armitage JO, Kastan MB, Doroshow JH, Tepper JE, eds. Abeloff's Clinical Oncology. 6th ed. Philadelphia, PA: Elsevier; 2020:chap 68.
National Comprehensive Cancer Network website. NCCN clinical practice guidelines in oncology (NCCN guidelines): Neuroendocrine and adrenal tumors. Version 2.2020. www.nccn.org/professionals/physician_gls/pdf/neuroendocrine.pdf. Updated July 24, 2020. Accessed November 11, 2020.
Strosberg JR, Al-Toubah T. Neuroendocrine tumors. In: Feldman M, Friedman LS, Brandt LJ, eds. Sleisenger and Fordtran's Gastrointestinal and Liver Disease. 11th ed. Philadelphia, PA: Elsevier; 2021:chap 34.
Updated by: Brent Wisse, MD, board certified in Metabolism/Endocrinology, Seattle, WA. Also reviewed by David Zieve, MD, MHA, Medical Director, Brenda Conaway, Editorial Director, and the A.D.A.M. Editorial team.
Your pancreas is an organ that’s found deep in your belly (abdomen) between your
stomach and spine. It helps you digest your food and controls your blood sugar by releasing a hormone called
insulin into your bloodstream. If your pancreas isn't working the way it should, or your body can't use the insulin it makes, your blood sugar levels get too high, and you get
diabetes. There is a connection between diabetes and other conditions of the pancreas, like pancreatitis or pancreatic cancer. But if you
have diabetes, you won't automatically have these other problems. And having these other issues doesn't mean for sure that you'll get diabetes. There are three common types of diabetes: Diabetes can sometimes be related to other problems with your pancreas. Pancreatitis is when your pancreas becomes
inflamed. It happens when proteins (enzymes) in your digestive system start to act while still in your pancreas and irritate its cells. While diabetes doesn’t cause pancreatitis, people with type 2 are at higher risk for it. There are several things that can cause pancreatitis, including infections and smoking. But the most common are heavy
alcohol use and gallstones, which are small masses in the gallbladder. Sometimes, the cause is unknown. There are two types of
pancreatitis:Diabetes and Pancreatitis
Symptoms of pancreatitis include: Doctors can treat pancreatitis. A serious case of it may force you to stay in the hospital. If you have type 2 diabetes, your body is more likely to be unable to process insulin, so you'll need even more insulin treatment. You can lower your risk by
losing weight or maintaining a healthy lifestyle, not smoking, and staying away from alcohol. Pancreatic cancer is a type of cancer that starts in the pancreas. Type 2 diabetes can have a link to it as either something
that raises your risk of having it or as a symptom. If you have type 2 diabetes, you're up to twice as likely to have pancreatic cancer as someone who doesn't have the condition. It's more likely to happen if you’ve had diabetes for a while -- 5 years or longer -- than if you don’t have it at all. If you have pancreatic cancer, but have had type 2 for less than 5 years, research hasn't figured out if the disease plays a role in the cancer or if the abnormal (precancerous) cells cause the
diabetes. It's rare, but pancreatic cancer can also cause diabetes, because it destroys the cells in the organ that make insulin. If you get type 2 diabetes when you're over age 50, it may be a symptom of pancreatic cancer. If you had it before this age, it could be a red flag if your blood sugar levels suddenly change after you've had them under control. Symptoms of this type of cancer don't usually happen until its later stages. If doctors have taken out all or
part of your pancreas to treat your pancreatic cancer (Whipple procedure), you can't make insulin anymore, and you'll end up with diabetes. Several things make it more likely that you'll get pancreatic cancer. You can change some of them, but others are out of your control. They include: Managing diabetes can be more difficult if you have pancreatic cancer. Doctors may change your medications or ask you to
check your blood sugar level more often. If cancer treatments have caused you to lose weight, the normal advice about diet and diabetes may not work for you. Talk to a diabetes or nutrition expert for more information about managing your condition.Diabetes and Pancreatic Cancer