Insulinoma:Symptoms, Causes and Diagnosis

Insulinoma is a tumor of the pancreas that produces excessive amounts of insulin.

Updated: September 29, 2019

Insulinoma is a tumor of the pancreas that produces excessive amounts of insulin. The tumors are usually less than 2cm and most often these are are non-cancerous. These kind of tumors are more common in women. Insulinomas produce excessive amounts of insulin causing low blood sugar level or hypoglesemia.
The typical symptoms related to low bloods sugar include tiredness, weakness, hunger. To prevent symptoms from the low blood sugar, you have to eat frequently. Psychiatric symptoms can also be developed because of the low blood sugar. 
The pancreas is an endocrine organ located behind your stomach. One of its functions is to produce insulin that control the level of sugar in your bloodstream. When your blood sugar drops too low, the pancreas stops creating insulin allowing your blood sugar levels to return to normal. When an insulinoma is formed in your pancreas, it will continue to produce insulin, even when your blood sugar is too low leading to hypoglycemia.

Symptoms of an Insulinoma:

People with insulinomas do not have noticeable symptoms unless it is severe. Mild symptoms include:

  • double vision or blurred vision
  • anxiety and irritability
  • sweating
  • dizziness
  • mood swings
  • weakness
  • tremors
  • hunger
  • sudden weight gain
  • confusion

More severe symptoms of insulinoma can affect the brain as well as the adrenal glands which regulate stress response and heart rate. Sometimes, symptoms seem similar to those of epilepsy which is a neurological disorder that causes seizures. Symptoms that are seen in more serious cases of insulinoma may include:

  • convulsions or seizures
  • a rapid heart rate which could be greater than 95 beats per minute
  • difficulty concentrating
  • loss of consciousness or coma

Insulinomas can get bigger and spread to other parts of the body. In this case you can get the following symptoms:

  • abdominal pain
  • back pain
  • diarrhea
  • jaundice, or yellowing of the skin and eyes

Causes of Insulinoma:

The pancreas creates insulin when you eat food that helps your body store the sugar from your food. The pancreas stops producing insulin once the sugar has been absorbed. This process usually keeps blood sugar levels stable. However, when an insulinoma develops, the tumor continues to produce insulin even when your blood sugar drops too low. This can lead to hypoglycemia.

Diagnosis of Insulinoma:

A blood test can be done to check your blood sugar and insulin levels. A low blood sugar level with a high insulin level indicates the presence of an insulinoma.
The test can also be done to check for other factors that include:

  • proteins that block the production of insulin
  • medications that cause the pancreas to release more insulin
  • other hormones that affect insulin production

A 72-hour fasting is required for this test. You will be hospitalized to better monitor your blood sugar levels. Your blood sugar levels will be measured at every six hours interval at least. You won't be able to eat or drink anything except water during the fast. You will likely develop very low blood sugar levels within 48 hours of starting the fast if you have an insulinoma.
Detection of the tumor in the pancreas may be difficult as most of these tumors are small in size.
Imaging tests such as a MRI or CT scan will help your doctor determine the location and size of the insulinoma. An endoscopic ultrasound may be advised if the tumor can't be found using the imaging test. In this test a long, flexible tube will be inserted into your mouth and down through the stomach and small intestine. The tube contains an ultrasound probe, which emits sounds waves that produce detailed images of your pancreas. Your doctor will take a small sample of tissue for analysis called biopsy once the insulinoma is located. This can be used to determine whether the tumor is cancerous.


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