Glucagon is a hormone normally secreted by the pancreas when blood glucose levels fall. Glucagon simulates the liver to break down stored carbohydrates to increase blood glucose. Glucagonomas are a type of pancreatic endocrine tumor. About 80% of glucagonomas are cancerous (malignant). However, they grow slowly, and many people survive for 15 years or more after the diagnosis. The average age at which symptoms begin is 50. About 80% of people with glucagonomas are women. A few people have multiple endocrine neoplasia.
High levels of glucagon in the blood cause the same symptoms as diabetes, such as weight loss and frequent, excessive urination. In addition, 90% of people have the very distinctive features of a chronic brownish red rash (called necrolytic migratory erythema) and a smooth, shiny, bright red-orange tongue. The mouth also may have cracks at the corners. The rash, which causes scaling, starts in the groin and moves to the buttocks, forearms, hands, feet, and legs.
The diagnosis of glucagonoma is made by identifying high levels of glucagon in the blood. Doctors then locate the tumor by doing computed tomography (CT) of the abdomen followed by endoscopic ultrasonography. Magnetic resonance imaging (MRI) or positron emission tomography (PET) may be used if the CT scan does not show a tumor.
Ideally, the tumor is surgically removed, which eliminates all symptoms. However, if removal is not possible or if the tumor has spread, chemotherapy may reduce the levels of glucagon and lessen the symptoms. However, chemotherapy does not improve survival.
The drug octreotide can be used to reduce glucagon levels, may clear up the rash, and may restore appetite, facilitating weight gain. But octreotide may elevate the levels of glucose in the blood even more.
Zinc taken by mouth, applied in an ointment, or given by vein (intravenously) may be used to treat the rash. Sometimes the rash is treated with intravenous amino acids or fatty acids.