What Is an Insulinoma?

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Insulinomas are rare tumors that form in the pancreas, an organ essential to enzyme and hormone production. One of these primary hormones is insulin, which helps metabolize food and regulates blood sugar. Insulinomas cause an overproduction of insulin, which can result in hypoglycemia, or low blood sugar.

Most insulinomas are noncancerous, and full recovery is often achieved when the tumor is surgically removed. This article will discuss the symptoms, causes, diagnosis, and treatment of insulinomas.

All about Insulinomas

Verywell / Theresa Chiechi

Types of Insulinomas

Insulinomas can be noncancerous (benign) or cancerous (malignant):

  • Noncancerous (benign): About 90% of all insulinomas are noncancerous tumors.
  • Cancerous (malignant): Cancerous insulinoma tumors are particularly rare, with little research done to date.

Most insulinoma tumors are solitary, meaning only one is found at a time, and they rarely spread to other parts of the body.

When insulinoma tumors are not solitary, surgically removing them as a form of treatment will be more challenging.

Insulinoma Symptoms

The typical symptoms of insulinoma can mimic hypoglycemia and other conditions, so it's important to speak with your physician about your symptoms in detail to get the most accurate diagnosis.

Symptoms of insulinoma can include:

  • Sweating
  • Heart palpitations
  • Tremors
  • Seizures
  • Confusion
  • Changes in personality or behavior
  • Blurry vision
  • On rare occasions, coma

Too much insulin can also result in hypoglycemia.

Causes

There isn't a known cause and many insulinomas are considered "sporadic."

There are, however, some risk factors that may contribute to the development of insulinoma. These include:

  • MEN-1: About 5%–10% of insulinoma tumors are associated with multiple endocrine neoplasia type 1 (MEN-1). The condition produces tumors or overactivity in the body's endocrine system, a series of glands that produce and secrete hormones. It has a genetic component, so having family members with MEN-1 increases the risk of developing the condition.
  • Inherited diseases: Insulinomas are more common in people with Von Hippel-Lindau syndrome, an inherited syndrome that produces tumors and cysts throughout the body, and people with neurofibromatosis type 1, which causes tumors to grow on nerves.
  • Demographic factors: Insulinomas are more common in women than men, and often appear in people between the ages of 40 and 60 years old.

Diagnosis

A diagnosis of insulinoma can be delayed for years because associated symptoms are similar to other conditions.

However, if insulinoma is suspected, a physician will supervise a period of fasting for about 48 hours. This is meant to bring on symptoms of hypoglycemia.

Follow-up tests are then ordered to measure levels of blood glucose, insulin, and insulin by-products (called C-peptides). Determining whether symptoms resolve or go away when glucose is given after fasting, or whether any medications may be increasing insulin, is also a part of the diagnostic process.

After the period of fasting and follow-up tests, computed tomography (CT), magnetic resonance imaging (MRI), or positron-emission tomography (PET) scans may be used to identify a tumor on the pancreas. If a tumor cannot be located using these imaging techniques, other, more invasive tests may be used to locate the tumor.

Treatment

Many insulinomas are treated successfully with surgery to remove the tumor.

Though there are several types of surgery that could be used, a less invasive procedure called laparoscopic surgery may be utilized to remove the tumor. In this procedure, the surgeon makes several small incisions using specialized surgical tools and a scope to see inside the body.

For tumors that cannot be surgically removed, dietary changes and medications to manage symptoms are typically prescribed. The same goes for cancerous insulinomas.

For those who have a cancerous insulinoma tumor, chemotherapy may also be used to shrink the tumor.

Nonsurgical Treatment for Insulinoma

In addition to dietary changes, eating smaller, more frequent meals each day can help prevent low blood sugar caused by the insulinoma. Medications such as Proglycem (diazoxide) or Sandostatin (octreotide) can be prescribed to reduce water retention and lower insulin production.

Prognosis

In most cases, surgical removal of a noncancerous insulinoma tumor will effectively cure the condition. The long-term survival rate is much higher for those with noncancerous insulinoma than those with malignant insulinoma.

Surgery can improve the survival rate for malignant tumors as well. But those who have MEN-1 or malignant insulinoma are more likely to experience recurrence of the tumors.

If surgical removal of the tumor is attempted and the majority of the pancreas is removed, diabetes will likely develop and require ongoing management.

A Word From Verywell

Insulinomas are very rare, and most are treatable. The symptoms associated with these tumors often mimic those of other conditions, so diagnosis can be challenging. If you are experiencing symptoms of insulinoma, discuss this with your healthcare provider. Fortunately, most insulinomas are benign, and surgical removal typically resolves any symptoms.

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