Insulinomas are insulin-producing tumors of the pancreas. A tumor is an abnormal new growth of tissue that results from rapid and uncontrolled multiplication of cells. The cells in a tumor have no beneficial purpose in the body and can be life-threatening. With 3 to10 cases per million people every year, insulinomas are the most common type of hormone-producing pancreatic tumor.
Causes, Risk Factors and Types of Insulimoma
The causes of insulinoma, and pancreatic cancer in general, are unknown. However, several factors that appear to increase the risk level include: heavy smoking; continual exposure to solvents, petroleum, and coal tar compounds; obesity; diabetes mellitus; diets rich in processed red meat; chronic inflammation of the pancreas, and certain genetic changes.
As with any other tumor, insulinomas can either be benign or malignant. In 90% of cases, insulinomas are benign, or non-cancerous, single tumors. About 10% of insulinomas are malignant, multiple tumors, with the potential to spread to other organs of the body. The word “cancer” generally refers to malignant tumors, which pose a greater danger to a person’s health.
Signs and Symptoms of Insulinoma
Because insulinomas produce high levels of insulin, blood sugar levels can drop below 50mg/dL, causing low-blood glucose crises (hypoglycemia). The symptoms of insulinoma are more likely to manifest a few hours after a meal, or early in the morning, and include the following:
- Abnormal behavior
- Amnesia
- Anxiety
- Blurred vision
- Confusion
- Dizziness
- Headache
- Hunger
- Pounding heartbeat
- Seizures
- Sweating
- Tremors
- Unconsciousness
- Weakness
Symptoms can be aggravated by exercise, alcohol, a low-calorie diet, and such drugs as sulfonylureas. Weight gain results in many cases, since affected people have to feed frequently to stop the low-blood sugar crises.
How Insulomas are Diagnosed
Because insulinomas are sometimes too small to be seen in CT scans, lab studies are usually the first step towards diagnosis. During a monitored 72-hour fast, blood may be tested for:
- Blood sugar concentration
- Blood insulin (and pro-insulin) levels
- C-peptide levels
- Screening for drugs like sulfonylurea, which causes the pancreas to release insulin
A CT or MRI scan of the abdomen may also be done to locate any tumor mass in the pancreas. Other tests used for diagnostic purposes include:
- An arteriography of the pancreas
- An endoscopic ultrasound
- Pancreatic venous sampling for insulin
Insulinoma Treatment and Complications
Since insulinoma surgery is successful in 90% of patients, it is currently the preferred therapy. A single tumor may be removed or, if there are several tumor masses, some of the pancreas may be removed through a procedure called “partial pancreatectomy.”
For cancerous insulinoma, or when a person cannot undergo surgery, medical therapy is necessary. The types of drugs used for treatment include:
- Hyperglycemic agents, such as Diazoxide, to block or slow insulin release from the insulinoma.
- Diuretics, to counter the swelling and other side effects caused by Diazoxide.
- Somatostatin analogs, to help control symptoms and insulin secretion.
- Antineoplastic agents, to keep tumor cells from growing and spreading further.
The two major complications of insulinoma are: severe hypoglycemia and the spread (metastasis) of a cancerous tumor. Both can result in death.
Early Intervention is Important
Besides the periodic symptoms of low-blood sugar they experience, people with insulinoma look normal. As a result, an insulinoma may exist for a week, months, or even years, before being diagnosed. Timely intervention is important because some insulinomas are cancerous, and can spread to other organs of the body with time. Secondly, unrecognized and unmanaged hypoglycemia can lead to irreversible neurologic damage. Seek care when symptoms of insulinoma develop, especially in cases of seizures and decreased consciousness.
References
eMedicine: Insulinoma; Zonera Ashraf Ali, MD. and Klaus Radebold, MD, PhD
Current Medical Diagnosis & Treatment; Stephen J. McPhee, Maxine A. Papadakis, Eds.; The McGraw-Hill Companies, 2009
Resources
Medline Medical Encyclopedia: Insulinoma
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