What is an insulinoma?

An insulinoma is a tumor on the pancreas. The pancreas makes insulin, which helps keep your blood sugar level balanced. Most of the time when your blood sugar level decreases, the pancreas stops making insulin to make sure that your blood sugar stays in the normal range. If you have a tumor on your pancreas called an insulinoma, it makes extra insulin. The tumor releases insulin independent of any food you eat. It makes more than your body can use. This causes blood sugar levels to drop too low. This type of tumor is rare. It usually doesn't spread to other parts of your body. Most insulinomas are not cancer.

What are the causes and risk factors for an insulinoma?

The cause of insulinomas is unknown. Usually no risk factor is identified. But women seem to be affected more often than men. Most often, insulinomas are found between ages 40 and 60. Some genetic diseases can raise your chance of getting an insulinoma. They are:

• Multiple endocrine neoplasia type 1, which is abnormal tissue growth in the endocrine system.

• Von Hippel-Lindau syndrome, an inherited disease that causes tumors and cysts throughout your body.

• Other genetic syndromes, such as neurofibromatosis type 1 and tuberous sclerosis.

What are the symptoms of an insulinoma?

An insulinoma can cause:

• Confusion.

• Sweating.

• Weakness.

• A rapid heartbeat.

• Anxiety.

• Clouded vision.

• Dizziness.

• Headaches.

• Tremor.

• Convulsions.

If your blood sugar gets too low, you can pass out and even go into a coma.

How is an insulinoma diagnosed?

Insulinomas are rare and can be hard to diagnose.

Blood tests. A 48- to 72-hour fast is the test commonly used for diagnosing insulinoma. If your health care provider thinks you have an insulinoma, you may stay in the hospital for a few days. This is so your provider can watch your blood sugar, insulin, C-peptide, and proinsulin during a 48- to 72-hour fast.

You will not be able to eat or drink anything except water during this time. If you have an insulinoma, you will probably have very low blood sugar levels within 48 hours of starting this test. If your symptoms of low blood sugar have been after meals, you may have a test of your blood sugar and insulin for several hours after a meal.

Imaging tests. These can help find out how big your tumor is and where it's located. A transabdominal ultrasound study is sometimes the first test done. Other tests include endoscopic ultrasound and PET or MRI scans. If the insulinoma is too small to be seen with these imaging tests, you may need tests that sample blood from multiple areas of your pancreas. These will find where the extra insulin is being released into your bloodstream.

How is an insulinoma treated?

Most insulinomas are not cancer. A surgeon can usually remove the tumor and cure the condition. This may be done using a laparoscope. In laparoscopy, the surgeon makes small incisions and uses special small tools to remove the tumor.

If your health care provider thinks that surgery would not be a good choice for you, there are other choices. These would help the symptoms of hypoglycemia. For example, you may need to eat small, frequent meals and take certain medicines to reduce the amount of insulin your body makes and to fight the effects of the excess insulin.

While you are waiting for your surgery, you may stay in the hospital and get intravenous (I.V.) solutions to keep you from becoming hypoglycemic. 

What are possible complications of an insulinoma?

After surgery to remove an insulinoma, some people develop a pancreatic fistula. This causes pancreatic fluid to leak. You may be given medicine and extra fluids to help your fistula heal. Most close without the need for more surgery.

Can an insulinoma be prevented?

There are no known ways to prevent an insulinoma. You may want to be checked for an insulinoma if any of your family members have any of the genetic conditions that increase risk.

Living with an insulinoma

Almost all insulinomas are not cancer. Removing the tumor usually cures the condition, and symptoms don't come back. You are unlikely to get diabetes unless your surgeon has to remove a large part of your pancreas.

A small number of insulinomas are cancer. Your surgeon may not be able to remove them entirely. If this happens, you may need to take medicine to help prevent hypoglycemia. You may also need chemotherapy to help control the size of the tumor.

When should I call my doctor?

If you have an insulinoma, you may have symptoms of low blood sugar. These include sweating, confusion, and double vision. You may notice these symptoms more when you’re hungry or after exercise. If you have these symptoms several times in 1 week, talk to your health care provider right away.

Key points about insulinomas

• An insulinoma is a tumor in your pancreas. It makes extra insulin, more than your body can use.

• An insulinoma can cause low blood sugar (hypoglycemia).

• Low blood sugar can cause confusion, sweating, weakness, and a rapid heartbeat. If your blood sugar gets too low, you can pass out and even go into a coma.

• Most insulinomas are not cancer.

• Removing the tumor usually cures the condition.

Next steps

Here are some tips to help you get the most from a visit to your health care provider:

• Know the reason for your visit and what you want to happen.

• Before your visit, write down questions you want answered.

• Bring someone with you to help you ask questions and remember what your provider tells you.

• At the visit, write down the name of a new diagnosis and any new medicines, treatments, or tests. Also write down any new instructions your provider gives you.

• Know why a new medicine or treatment is prescribed and how it will help you. Also know what the side effects are and when they should be reported.

• Ask if your condition can be treated in other ways.

• Know why a test or procedure is recommended and what the results could mean.

• Know what to expect if you don't take the medicine or have the test or procedure.

• If you have a follow-up appointment, write down the date, time, and purpose for that visit.

• Know how you can contact your health care provider if you have questions, especially after office hours and on weekends.