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

The pancreas is an organ in the abdomen that makes the hormone insulin. Insulin is necessary to regulate blood sugar levels. Tumors of the pancreas that produce too much insulin (hyperinsulinemia) are called insulinomas.

High insulin levels cause low blood sugar levels (hypoglycemia). Hypoglycemia may be mild, leading to symptoms such as anxiety and hunger, or severe, leading to seizures, coma, and even death.

Insulinomas are rare tumors. They usually occur as single, small tumors in adults. They are very rare in children. Most children with hyperinsulinism have multiple areas of overactive insulin-secreting cells in the pancreas, rather than a single tumor.

Most insulinomas are benign -- only 5 to 10 percent are cancerous. People with the genetic syndrome called multiple endocrine neoplasia Type I (MEN I) are at risk for developing insulinomas.

• Sweating
• Tremor
• Rapid heart rate
• Anxiety
• Hunger
• Dizziness
• Headache
• Clouded vision
• Confusion
• Behavioral changes
• Convulsions
• Loss of consciousness

The person's blood may be tested after fasting for:

• Low blood glucose
• High blood insulin level
• High C-peptide level

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

• Endoscopic ultrasound
• Octreotide scan
• Pancreatic arteriography
• Pancreatic venous sampling for insulin

Surgery is the normal treatment for insulinoma. The location of the tumor is determined by diagnostic tests or surgical exploration. A single tumors will be removed, but multiple tumors usually require partial removal of the pancreas (partial pancreatectomy). At least 15% of the pancreas is left to produce the pancreatic enzymes necessary to prevent nutrient malabsorption.

If no tumor is found during surgery, or the patient is not a candidate for surgery, the drug diazoxide may be given to lower insulin secretion and avoid hypoglycemia. A diuretic (water pill) is given with this medication to prevent the body from retaining fluid.

Octreotide is used to suppress insulin secretion in some patients. Medication is also used to stabilize the patient prior to surgery.

In a majority of cases, the tumor is benign, and surgery is effective in resolving the disease. However, a severe hypoglycemic reaction or the spread of a cancerous tumor to other organs can be fatal.

• Severe hypoglycemic reaction
• Spreading of a cancerous tumor (metastasis)

Call your health care provider if you develop any symptoms of insulinoma. Convulsions and decreased consciousness are an emergency. Call 911.