Introduction:
Insulinomas are rare endocrine tumors that cause the overproduction of insulin. This excessive insulin causes hypoglycemia. Most insulinomas are benign, and only some of these tumors become malignant. The exact cause of this disease is still unknown, but there are a few factors like Von Hippel-Lindau disease that increases the risk of developing insulinomas. Symptoms of insulinomas are associated with hypoglycemia like feeling hungry, weight gain, anxiety, nausea, palpitation, tremors, etc. In addition, the patient also shows symptoms due to a shortage of glucose in the brain, which includes seizures, confusion, blurred or double vision, recurrent headaches, and lethargy.
What Are the Pancreas and Insulin?
The pancreas is an organ (and gland) located at the back of the stomach; it is a part of the digestive system. The pancreas performs exocrine and endocrine functions. The exocrine function includes the production of enzymes (lipase, amylase, and protease) that helps in the digestion of food. At the same time, the endocrine functions include the secretion of insulin and glucagon. Insulin is a hormone that is responsible for the regulation of blood sugar levels in the body. Insulin allows the glucose in the blood to enter the cells and, therefore, provides them the energy to function. Any disorder in the pancreas can lead to an imbalance in the levels of these enzymes and hormones, resulting in multiple systemic complications.
What Is Insulinoma?
Insulinoma is a tumor of the pancreas that causes excess insulin production from the gland. These tumors are derived from the pancreatic islet beta cells, responsible for synthesizing and secreting insulin and amylin. Therefore, insulinomas cause overproduction of insulin, causing hypoglycemia. These tumors are a rare form of neuroendocrine tumor, but they are the most common functioning endocrine neoplasm of the pancreas; it represents one to two percent of all pancreatic tumors. Most insulinomas are either present in the pancreas or directly attached to the pancreas. Insulinomas are small tumors approximately less than two centimeters in diameter. Insulinomas are primarily benign, but about five to thirty percent of all insulinomas can be cancerous.
Who Is More Affected by Insulinomas?
-
Insulinomas are a rare form of neuroendocrine tumor, and they affect approximately one to four people per million.
-
Insulinomas can occur at any age; therefore, there is no increased disease incidence in older patients.
-
Insulinomas affect men and women equally.
-
People affected by Von Hippel-Lindau disease (VHL) are at higher risk of developing insulinoma because this disease causes tumors and cysts to form throughout the body.
What Causes Insulinoma?
The definitive cause of insulinoma is still unknown. These tumors arise randomly without any warning.
What Are the Symptoms of Insulinoma?
The following signs and symptoms are commonly seen in a patient with insulinoma:
-
Symptoms associated with hypoglycemia (low blood sugar levels).
-
The patient develops neuroglycopenic symptoms (shortage of glucose in the brain) like recurrent headaches, lethargy, diplopia (double vision), etc.
-
Anxiety and behavior changes.
-
In case of severe hypoglycemia, the patient can go into comatose (condition of prolonged unconsciousness).
-
Seizures and convulsions.
-
Unusual weight gain.
-
Feeling hungry between meals.
-
Increased heart rate and palpitations.
-
Nausea and vomiting.
-
Excessive sweating.
-
In some instances, the tumor grows bigger and results in abdominal pain, back pain, diarrhea, and jaundice.
How Are Insulinomas Diagnosed?
Insulinomas can be tricky to diagnose because the average time between the start of symptoms and diagnosis is usually three years. Therefore, the following tests are done to confirm the diagnosis of insulinomas:
-
Blood Tests- Blood samples are collected and sent to the laboratory to evaluate insulin, glucose, and C-peptide. Sometimes, proinsulin levels are also checked.
-
Suppression Test- The patient is supposed to fast for 72 hours, but calorie-free and caffeine-free liquids may be given during this test. Blood samples are collected every four hours until the blood glucose level is less than 60 mg/dL. Then the blood samples are collected every hour until the values are less than 49 mg/dL. After hypoglycemia, blood samples are collected, and the insulin, glucose, C-peptide, and proinsulin levels are evaluated.
-
Imaging Tests- Non-invasive imaging tests are done to determine the location and size of the tumor. Ultrasounds, CT scans (computed tomography), and MRI (magnetic resonance imaging) are used to localize the tumors. Endoscopic ultrasounds are also done.
What Is the Treatment of Insulinoma?
-
Surgical removal of insulinoma is the definitive treatment of the disease. Sometimes, parts of the pancreas are also removed, along with tumors.
-
Medications like Diazoxide and Somatostatin are also used to block the release of insulin in patients who cannot undergo a surgical procedure.
-
Hepatic arterial occlusion (blocking the blood flow of the liver) or embolization methods are used in cancerous tumors with growth within the liver.
-
When the tumor is cancerous, radiofrequency ablation, chemotherapy, and cryotherapy may be used in rare cases.
What Are the Complications of Insulinoma?
Mentioned below are the possible complications of insulinomas:
-
Severe hypoglycemia.
-
Spread of the cancerous tumor to other parts of the body.
-
Diabetes, in patients whose entire pancreas is removed during the surgical treatment.
-
Inflammation of the pancreas.
-
Some patients, after surgery, may develop a pancreatic fistula. This causes pancreatic fluids to leak.
What Is the Prognosis of Insulinoma?
The majority of the insulinomas are non-cancerous, and surgical removal of the tumor successfully addresses the condition. Most patients recover uneventfully after the surgery. However, these tumors can recur in the case of patients with multiple insulinomas. In addition, some patients may develop diabetes after their whole pancreas is removed. A hypoglycemic reaction or tumor spread can create a life-threatening condition in the worst cases.
Conclusion:
Insulinomas are rare endocrine tumors of the pancreas that cause excess insulin production. Most of these tumors are benign (non-cancerous). The diagnosis of the tumor is based on blood examinations and image testing. At the same time, the definitive treatment of insulinoma is the surgical removal of the tumor. If left untreated for a long time, this condition can progress into a life-threatening disease. Therefore, it is advised to consult an expert physician when similar symptoms to insulinomas are seen.
