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Insulinoma

Insulinoma; Islet cell adenoma, Pancreatic neuroendocrine tumor; Hypoglycemia - insulinoma

 

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

Causes

 

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. 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 risk for insulinomas.

 

Symptoms

 

Symptoms are most common when you skip or delay a meal. Symptoms may include:

  • Anxiety, behavior changes, or confusion
  • Clouded vision
  • Loss of consciousness or coma
  • Convulsions or tremor
  • Dizziness or headache
  • Hunger or weight gain
  • Fast heart rate
  • Sweating

 

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
  • 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 cancer 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 exact location of the tumor that is making too much insulin)

 

Treatment

 

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 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 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.

 

Outlook (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.

 

Possible Complications

 

Complications may include:

  • Severe hypoglycemic reaction
  • Spread of a cancerous tumor (metastasis)
  • Diabetes if the entire pancreas is removed (rare)
  • Inflammation and swelling of the pancreas

 

When to Contact a Medical Professional

 

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

 

 

References

Jensen RT, Norton JA, Oberg K. Neuroendocrine tumors. In: Feldman M, Friedman LS, Brandt LJ, eds. Sleisenger and Fordtran's Gastrointestinal and Liver Disease: Pathophysiology/Diagnosis/Management. 10th ed. Philadelphia, PA: Elsevier Saunders; 2016:chap 33.

National Comprehensive Cancer Network. NCCN Clinical Practice Guidelines in Oncology (NCCN Guidelines): Neuroendocrine tumors. Version 2.2016. www.nccn.org/professionals/physician_gls/pdf/neuroendocrine.pdf. Accessed August 18, 2016.

Schneider DF, Mazeh H, Lubner SJ, Jaume JC, Chen H. Cancer of the endocrine system. In: Niederhuber JE, Armitage JO, Doroshow JH, Kastan MB, Tepper JE, eds. Abeloff's Clinical Oncology. 5th ed. Philadelphia, PA: Elsevier Churchill Livingstone; 2014:chap 71.

 
  • Endocrine glands

    Endocrine glands - illustration

    Endocrine glands release hormones (chemical messengers) into the bloodstream to be transported to various organs and tissues throughout the body. For instance, the pancreas secretes insulin, which allows the body to regulate levels of sugar in the blood. The thyroid gets instructions from the pituitary to secrete hormones which determine the pace of chemical activity in the body (the more hormone in the bloodstream, the faster the chemical activity; the less hormone, the slower the activity).

    Endocrine glands

    illustration

  • Food and insulin release

    Food and insulin release - illustration

    Insulin is a hormone secreted by the pancreas in response to increased glucose levels in the blood.

    Food and insulin release

    illustration

    • Endocrine glands

      Endocrine glands - illustration

      Endocrine glands release hormones (chemical messengers) into the bloodstream to be transported to various organs and tissues throughout the body. For instance, the pancreas secretes insulin, which allows the body to regulate levels of sugar in the blood. The thyroid gets instructions from the pituitary to secrete hormones which determine the pace of chemical activity in the body (the more hormone in the bloodstream, the faster the chemical activity; the less hormone, the slower the activity).

      Endocrine glands

      illustration

    • Food and insulin release

      Food and insulin release - illustration

      Insulin is a hormone secreted by the pancreas in response to increased glucose levels in the blood.

      Food and insulin release

      illustration


     

    Review Date: 8/7/2016

    Reviewed 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.

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