This page was reviewed under our medical and editorial policy by
Toufic Kachaamy, MD, Chief of Medicine, City of Hope Phoenix
This page was updated on May 26, 2023.
An insulinoma is a type of pancreatic neuroendocrine tumor (NET). Neuroendocrine cells produce hormones and forge small groups called islets. Pancreatic NETs are either functioning or nonfunctioning; functioning NETs release hormones into your bloodstream. Different types of neuroendocrine cells release different types of hormones. For example, insulinomas grow from insulin-producing cells.
Insulin lowers levels of glucose, or sugar, in your blood. Because insulinomas produce too much of the hormone, this may cause low blood sugar levels.
Insulinomas may be either malignant (cancerous) or benign (noncancerous). Though insulinomas are the most common functioning pancreatic NETs, only 1 percent to 2 percent of all pancreatic tumors are insulinomas, and up to 90 percent are benign, according to a review in the World Journal of Gastroenterology.
When your body produces too much insulin, your blood sugar becomes too low, a condition called hypoglycemia. This is the most common symptom of insulinomas.
You may also experience the following symptoms if you have an insulinoma:
At dangerously low blood sugar levels, symptoms may escalate, causing you to faint, have seizures or go into a coma. In extreme cases, death may occur.
While the exact cause of insulinomas remains unknown, patients with certain genetic syndromes are more likely to develop NETs (such as insulinomas), as these result from specific DNA mutations.
Multiple endocrine neoplasia type 1 (MEN1) syndrome: This inherited condition raises the risk of pancreatic and other types of NETs because of changes to the MEN1 gene. MEN1 gene mutations are the most common cause of inherited NETs.
Von Hippel-Lindau (VHL) syndrome: This condition causes mutations to the VHL gene that may result in pancreatic NETs.
Neurofibromatosis type 1 (NF1) syndrome: Changes to the NF1 gene cause a small portion of pancreatic NETs.
Tuberous sclerosis: This condition causes tumors to develop.
While the presence of risk factors increases your odds of developing pancreatic NETs such as insulinomas, there’s no way to know for sure whether it will happen. Below, find risk factors that are associated with a greater chance of developing insulinomas.
Age: The most common age range for a diagnosis of pancreatic NETs such as insulinomas is between 50 to 60 years old.
Smoking: Smoking increases the risk of developing insulinomas.
Alcohol: Heavy drinking has been associated with an increase of pancreatic NETs.
Diabetes: People with diabetes, a condition that makes blood sugar levels increase, are at increased risk of insulinomas and other pancreatic NETs.
Family history: If a close relative has or had cancer, the risk increases.
Diagnosing insulinomas may be difficult because the symptoms of low blood sugar (hypoglycemia) that patients experience occur with other conditions as well.
First, your doctor measures your blood sugar and insulin levels. Most often, a 72-hour fasting test conducted at a hospital is necessary to measure fasting blood glucose levels of insulin, proinsulin and C peptide. During this time, you may only drink water. Tests are conducted every four to six hours for the duration of your hospital stay.
If an insulinoma is detected, a computed tomography (CT) scan can help pinpoint the location and extent of your tumor, and a magnetic resonance imaging (MRI) scan can determine if it’s spread.
Sometimes, an ultrasound is combined with an endoscopy in a procedure called an endoscopic ultrasound (EUS) scan. During this scan, your care team will use an endoscope, a long thin tube with a lighted camera on one end, to check your esophagus, stomach, pancreas and bile duct for suspicious areas.
Radioactive scans such as Gallium Ga-68 DOTATATE PET/CT also may be conducted to illuminate NET cells, which absorb a radioactive substance injected into your body before the scan.
Treatment depends on the size and location of your tumor. Most often, surgery is an appropriate treatment for insulinomas.
Surgical procedures include:
Enucleation: Usually done laparoscopically (via small incisions) during a procedure called keyhole surgery, the entire tumor is removed with the help of surgical tools and a laparoscope, a thin, tube-like instrument with a lighted camera on one end.
Distal pancreatectomy: The tail and a portion of the body of the pancreas are removed if the tumor is limited to these areas. Typically, the spleen is removed also. The procedure can be done via open surgery (one large incision) or laparoscopically.
Whipple procedure (pancreaticoduodenectomy): This type of surgery removes the head of the pancreas as well as nearby affected organs that may include the gallbladder, lymph nodes, and part of the bile duct, stomach and/or small intestines. This may be done via open surgery (most common) or laparoscopically.
Additional treatments include:
Drugs: If you’re not healthy enough to have surgery or the tumor has spread, you may be given medications to reduce the amount of insulin your body produces, such as diazoxide, prednisolone, verapamil and diphenylhydantoin. Somatostatin analogs such as Sandostatin® (octreotide) and Somatuline Depot® (lanreotide) may be given to help lower your insulin levels.
Diet: In some cases, your doctor may ask you to follow a diet high in certain carbohydrates and/or eat more frequently to increase your blood glucose levels.
Chemotherapy: If you have a cancerous insulinoma that has spread to other areas of your body, chemotherapy may be warranted.
Radiofrequency ablation (RFA): If your melanoma is limited to the pancreas and you cannot have surgery, a procedure using heat from radio waves may be used to fight cancer cells.
Trans-arterial embolization (TAE): If your insulinoma has spread to the liver, your doctor may recommend this treatment, in which a gel is injected to block the supply of blood to the liver. This procedure may also be used to deliver high doses of chemotherapy exclusively to the tumor.
Clinical trials: New research is always being done to test the efficacy of existing treatments and develop new ones. If a clinical trial is available and you're interested in participating, ask your doctor if it’s right for you.
Among tumors that can be fully removed, there’s almost a 100 percent rate of success, according to a review in Research and Reports in Endocrine Disorders.
Metastatic insulinomas account for 5 percent to 12 percent of all insulinomas, and the survival rate when insulinomas spread to lymph nodes or to the liver is about two years.