Alternate Names: Insuloma; Islet cells adenoma

Causes and Risks:

The pancreas is an organ in the abdomen that releases the hormone insulin. Insulin is required to regulate blood levels of the sugar glucose. Tumors of the pancreas that produce excessive amounts of insulin (hyperinsulinemia) are called insulinomas.

High insulin levels cause hypoglycemia, or low blood glucose. Hypoglycemia caused by insulinomas may be mild and lead to symptoms such as anxiety and hunger, but patients are also at risk for severe hypoglycemia that can cause seizures, coma and even death.

Insulinomas are rare tumors that occur in about 1 out of 250,000 people. They usually occur as single, small tumors in adults, though the majority of children with hyperinsulinemia do not have a discrete tumor.

Five to ten percent of insulinomas are malignant. Patients diagnosed with multiple endocrine neoplasia, Type I (MENI), are at risk to develop insulinomas.

Prevention:

There is no known way to prevent the development of an insulinoma.

Symptoms:

• sweating
• tremor
• rapid heart rate
• anxiety
• hunger
• dizziness
• headache
• clouding of vision
• confusion
• behavioral changes
• convulsions
• loss of consciousness

Signs and Tests:

• during a monitored fast:
  • low blood glucose
  • high serum insulin level
  • high C-peptide level
• CT scan or MRI of the abdomen to look for a pancreatic tumors
• Octreotide scan to look for pancreatic tumors (when CT or MRI scan is unrevealing)
• Pancreatic arteriography (when CT or MRI scan is unrevealing)
• Pancreatic venous sampling for insulin (when CT or MRI scan is unrevealing)

Treatment:

Surgery is the preferred treatment for insulinoma. The tumor is localized with diagnostic testing or surgical exploration. Solitary tumors are resected, but patients with multiple tumors usually require partial resection of the pancreas (partial pancreatectomy). At least 15% of the pancreas is left to avoid malabsorption due to lack of pancreatic enzymes.

If no tumor is found at surgery or a patient is not a candidate for surgery, the drug diazoxide may be given to lower insulin secretion and avoid hypoglycemia. A diuretic is always given with this medication to avoid retaining too much salt. Medical treatment is also used to stabilize the person prior to surgery.

Prognosis:

Death may result from a severe hypoglycemic reaction or spread of malignant tumors to other organs (metastases).

Complications:

• severe hypoglycemic reaction
• tumor metastasis

Call your health care provider if symptoms of insulinoma develop. Convulsions and decreased consciousness are emergency symptoms.