Insulinoma

Insuloma; Islet cell adenoma

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.

90% of insulinomas are non-cancerous (benign) tumors. People with specific genetic syndromes such as multiple endocrine neoplasia type I are at risk of insulinomas and other endocrine tumors.

When you have an insulinoma, you may have any of the following symptoms:

• 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

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

Abdomen CT, MRI, 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:

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

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.