These tumors arise from cells in the pancreas that produce insulin.
Symptoms caused by low blood sugar (hypoglycemia Hypoglycemia Hypoglycemia is abnormally low levels of sugar (glucose) in the blood. Hypoglycemia is most often caused by drugs taken to control diabetes. Much less common causes of hypoglycemia include other... read more ) include faintness, weakness, headache, and confusion.
Diagnosis includes blood and imaging tests.
Treatment is surgery and sometimes chemotherapy.
Insulinomas are a type of pancreatic endocrine tumor Overview of Pancreatic Endocrine Tumors The pancreas is an organ located in the upper part of the abdomen. It produces digestive juices that are secreted into the digestive tract. The pancreas also produces insulin, which helps control... read more . Only 10% of insulinomas are cancerous. The average age at diagnosis is 50.
Symptoms of insulinoma result from low levels of sugar (glucose) in the blood (hypoglycemia Hypoglycemia Hypoglycemia is abnormally low levels of sugar (glucose) in the blood. Hypoglycemia is most often caused by drugs taken to control diabetes. Much less common causes of hypoglycemia include other... read more ), which occur when the person does not eat for several hours (most often in the morning after an all-night fast). The symptoms include faintness, weakness, trembling, awareness of the heartbeat (palpitations), sweating, nervousness, and profound hunger. Other symptoms include headache, confusion, vision abnormalities, unsteadiness, and marked changes in personality. The low levels of sugar in the blood may even lead to a loss of consciousness, seizures, and coma.
Diagnosing an insulinoma can be difficult. Doctors try to do blood tests while the person has symptoms and has not eaten. Blood tests include measurements of blood glucose levels and insulin levels. Very low levels of glucose and high levels of insulin in the blood indicate the presence of an insulinoma. Because many people have symptoms only occasionally, doctors may admit them to the hospital. In the hospital, the person fasts for at least 48 hours, sometimes up to 72 hours, and is closely monitored. During that time, the symptoms usually appear, and blood tests are done to measure the levels of glucose and insulin.
If the blood tests suggest the person has an insulinoma, the location must then be pinpointed. Imaging tests, such as endoscopic ultrasonography Ultrasound Scanning (Ultrasonography) of the Abdomen Ultrasound scanning uses sound waves to produce pictures of internal organs (see also Ultrasonography). An ultrasound scan can show the size and shape of many organs, such as the liver and pancreas... read more (which shows the lining of the digestive tract more clearly because the ultrasound probe is placed on the tip of the endoscope) or positron emission tomography Positron Emission Tomography (PET) Positron emission tomography (PET) is a type of radionuclide scanning. A radionuclide is a radioactive form of an element, which means it is an unstable atom that becomes more stable by releasing... read more (PET) scans, can be used to locate the tumor, but sometimes exploratory surgery is needed.
The primary treatment for an insulinoma is surgical removal, which has a cure rate of about 90%.
When the insulinoma cannot be completely removed and symptoms continue, drugs such as diazoxide or sometimes octreotide can help keep blood glucose from falling too low. Chemotherapy drugs may help control the tumor.