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Insulinoma

An insulinoma is a tumor in the pancreas that produces too much insulin.

Alternative Names

Insuloma; Islet cell adenoma

Causes, incidence, and risk factors

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 it move into cells.

Most of the time when your blood sugar level drops too low, the pancreas stops making insulin until your blood sugar returns to normal. Tumors of the pancreas that produce too much insulin are called insulinomas. Insulinomas keep making insulin, even when your blood sugar drops too low.

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 rare tumors. They usually occur as single, small tumors in adults.

These tumors are very rare in children. Most children with high blood insulin levels have many areas of overactive insulin-releasing cells in the pancreas, instead of a single tumor.

More than 90% of insulinomas are non-cancerous (benign) tumors. People with the genetic syndrome called multiple endocrine neoplasia type I are at risk of insulinomas and other endocrine tumors .

Symptoms

Signs and tests

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

CT or MRI scan of the abdomen , or PET scan  may be done to look for a tumor in the pancreas. If the test is negative, one of the following tests may be performed:

Treatment

Surgery is the recommended treatment for insulinoma. The tumor is first found by tests or surgery. Medication may be used to get patients stable before surgery.

If there is a single tumor, it will be removed. If there are many tumors, part of the pancreas will need to be removed (partial pancreatectomy). At least 15% of the pancreas must be left to produce its enzymes for digestion. This may prevent the surgeon from removing the whole insulinoma tumor.

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 injections are then required.

If no tumor is found during surgery, or if you are not a candidate for surgery, you may get the drug diazoxide to lower insulin production and prevent hypoglycemia. A diuretic (water pill) is given with this medication to prevent the body from retaining fluid. Octreotide is used to reduce insulin release in some patients.

Expectations (prognosis)

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

  • Severe hypoglycemic reaction
  • Spreading of a cancerous tumor (metastasis )
  • Diabetes if the entire pancreas is removed (rare)

Calling your health care provider

Call your health care provider if you develop any symptoms of insulinoma. Convulsions and decreased consciousness are an emergency -- call 911 or your local emergency number right away.

References

Cryer PE. Hypoglycemia. In: Shlomo M, Polonsky KS, Larsen PR, Kronenberg HM, eds. Williams Textbook of Endocrinology. 12th ed. Philadelphia, PA: Elsevier Saunders; 2011:chap 34.

Jensen RT, Norton JA. Endocrine tumors of the pancreas and gastrointestinal tract. In: Feldman M, Friedman LS, Brandt LJ, eds. Sleisenger and Fordtran's Gastrointestinal and Liver Disease. 9th ed. Philadelphia, PA: Elsevier Saunders; 2010:chap 32.

National Cancer Institute: PDQ Pancreatic neuroendocrine tumors (islet cell tumors) treatment. Bethesda, MD: National Cancer Institute. Date last modified 11/10/2012. Available at: http://www.cancer.gov/cancertopics/pdq/treatment/pancreatic/HealthProfessional. Accessed January 3, 2013.

Updated: 12/22/2012

Nestoras Mathioudakis, MD, Assistant Professor of Medicine, Division of Endocrinology & Metabolism, Johns Hopkins School of Medicine, Baltimore, MD. Review provided by VeriMed Healthcare Network. Also reviewed by A.D.A.M. Health Solutions, Ebix, Inc., Editorial Team: David Zieve, MD, MHA, David R. Eltz, Stephanie Slon, and Nissi Wang.


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