Insulinoma

What is insulinoma?

Insulinoma is a rare tumor in your pancreas that releases excess insulin. Insulin is the hormone that helps keep your blood sugar (glucose) at healthy levels.

Insulinoma is one of several pancreatic neuroendocrine tumors (pNETs). These are rare tumors that start in your pancreas’s endocrine cells.

About 85% to 90% of insulinomas are nonmetastatic (“indolent”). This means they don’t spread outside of your pancreas (metastasize). Metastatic (“aggressive”) insulinomas are very rare. Metastatic insulinomas are most likely to spread to your lymph nodes and/or liver.

How does insulinoma affect my body?

Insulinomas release insulin. If you have insulinoma, it typically floods your body with insulin. This results in low blood sugar (hypoglycemia). When that happens, you may feel shaky. You may also feel like your heart is racing. In extreme circumstances, you may faint or have seizures.

Your symptoms should improve if you consume something that has sugar (carbohydrates). This could include apple juice, regular soda or a banana.

Experiencing low blood sugar can be scary, especially when you don’t know why it’s happening or when it’ll strike again. Keep snacks on hand and see your healthcare provider as soon as possible.

What are the symptoms of insulinoma?

Insulinomas mainly cause low blood sugar (hypoglycemia) episodes. Symptoms of low blood sugar include:

• Confusion or difficulty concentrating
• Sweating
• Rapid heartbeat
• Anxiety or irritability

Symptoms of severe low blood sugar include:

• Vision changes, like blurred vision
• Slurred speech
• Clumsiness or difficulty with coordination
• Seizures
• Loss of consciousness

Most people with insulinoma experience low blood sugar when fasting — usually in the morning when they wake up. Some people with insulinoma experience low blood sugar episodes after meals.

Persistent hypoglycemia can interfere with daily activities and cause irreversible brain damage. It can even lead to coma and death. It’s very important to see your healthcare provider if you have low blood sugar symptoms.

What causes insulinoma?

Insulinomas happen when the cells in your pancreas that create insulin multiply uncontrollably. Researchers aren’t sure why that happens.

But they do know that insulinoma can happen alongside multiple endocrine neoplasia type 1 (MEN1). This is an inherited condition in which multiple tumors affect different parts of your endocrine system. About 5% to 10% of insulinoma cases affect people with MEN1.

If one of your first-degree relatives (biological parents and siblings) has a MEN1 diagnosis, talk to your healthcare provider. They can recommend genetic testing that can screen for the condition. If you have MEN1, genetic testing could help detect tumors in their early phases.

How do healthcare providers diagnose insulinoma?

Your healthcare provider will likely suspect you have insulinoma if you have the following signs (called Whipple’s triad):

• Symptoms of low blood sugar
• A documented low blood sugar test result (a fingerstick blood sugar result at least less than 55 mg/dL)
• Improvement of your symptoms when you eat or drink sugar (carbohydrates)

They’ll then recommend some tests to help diagnose insulinoma.

72-hour fast

Your provider may recommend fasting up to 72 hours to bring on a low blood sugar episode. This is the gold-standard test for diagnosing insulinoma. But you won’t be alone. A provider will monitor you during your fast.

Once you develop low blood sugar symptoms, you’ll get blood tests that check your:

• Blood sugar level
• Insulin level
• Proinsulin level
• C-peptide level
• Beta-hydroxybutyrate level
• Sulfonylurea level

After the blood draw, a provider will give you treatment for the low blood sugar.

The results of these tests can show if too much insulin (hyperinsulinemia) is causing your low blood sugar episodes.

Imaging tests

If the 72-hour fast points to insulinoma, your provider may suggest one or more of the following imaging tests:

• CT scan
• MRI scan
• Abdominal ultrasound
• Endoscopic ultrasound (EUS)

These tests can assess the tumor’s size and its location in your pancreas. If imaging tests don’t provide enough information, your provider may recommend a selective arterial calcium stimulation test. For this test, a provider measures insulin levels in your hepatic (liver) vein after stimulating arteries in various parts of your pancreas.

What is the treatment for insulinoma?

Surgery is the main treatment for nonmetastatic (indolent) insulinomas. Surgical options include:

• Enucleation. Your surgeon removes the insulinoma without cutting into it. This is kind of like the way you might remove the yolk from a hard-boiled egg.
• Partial pancreatectomy. As the name sounds, this surgery involves removing part of your pancreas. In this case, it’s the part where the insulinoma is.
• Whipple surgery. Your surgeon removes part of your pancreas and other nearby tissues. You may need this surgery if the insulinoma is metastatic.

Each of these surgeries has different risks. Your provider will go over the risks and which surgery would be best for you.

Prevention and treatment of low blood sugar (hypoglycemia)

In the time leading up to surgery (or if surgery isn’t possible), it’s important to prevent and treat low blood sugar episodes. Your provider may recommend getting a continuous glucose monitoring (CGM) system. A CGM can help you catch low blood sugar episodes before they get too severe, especially during the night.

It’s important to remember that you shouldn’t use a CGM to diagnose insulinoma or other low blood sugar conditions. They’re for monitoring conditions after a diagnosis.

Your provider may recommend one or more of the following treatments for low blood sugar:

• Dietary changes. Regular meals or snacks rich in complex carbohydrates can help prevent low blood sugar. A bedtime or late-night meal may also help.
• IV glucose. If you experience frequent severe episodes of hypoglycemia, you may need to receive IV glucose.
• Diazoxide. This medication can help control how much insulin your pancreas releases. It may also increase how much glucagon your liver releases. Glucagon raises your blood sugar.
• Octreotide and lanreotide. These medications may help reduce the release of insulin from certain types of insulinoma tumors.

It’s important to wear medical identification that states that you experience low blood sugar. This way, someone can get you help as soon as possible if you have a severe episode. Also, tell people close to you about your low blood sugar episodes and how they can help.

Treatment of metastatic insulinoma

Your provider may recommend combining surgery with other treatments for metastatic (aggressive) insulinoma. Or they may use medical treatments when surgery isn’t an option. Your provider might recommend:

• Peptide receptor radionuclide therapy (PRRT)
• Targeted therapy
• Chemotherapy

Can insulinoma be cured?

Yes, most insulinomas can be cured with surgery. One study showed that 87% of people who had surgery for nonmetastatic insulinoma were alive 10 years after diagnosis. Your healthcare provider will consider factors like the tumor’s size and location before recommending a specific surgery.

The 10-year survival rate for metastatic insulinomas was 33%. It’s important to remember this is just an estimate. Your healthcare team will be able to give you a better idea of what to expect based on your unique situation.