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 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.
Exams 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
Surgery is the recommended treatment for insulinoma. Medicines may be used to get people 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). 15% of the pancreas must be left to produce its 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 injections are then required.
If no tumor is found during surgery, or if you are not a candidate for surgery, you may get the medicine diazoxide to lower insulin production and prevent hypoglycemia. A diuretic (water pill) is given with this medicine to prevent the body from retaining fluid. Another medicine, octreotide, 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
- Spreading of a cancerous tumor (metastasis)
- Diabetes if the entire pancreas is removed (rare)
When to Contact a Medical Professional
Call your health care provider if you develop any symptoms of insulinoma. Convulsions and losing consciousness are an emergency. Call 911 or your local emergency number right away.
Insuloma; Islet cell adenoma
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 07/31/2014. Available at: www.cancer.gov/cancertopics/pdq/treatment/pancreatic/HealthProfessional. Accessed October 25, 2014.
Review Date 10/25/2014
Updated by: Brent Wisse, MD, Associate Professor of Medicine, Division of Metabolism, Endocrinology & Nutrition, University of Washington School of Medicine, Seattle, WA. Also reviewed by David Zieve, MD, MHA, Isla Ogilvie, PhD, and the A.D.A.M. Editorial team.