There is frequently a long delay between the initial symptoms and the diagnosis. The 90 percent of the non-functioning tumors that are malignant produce symptoms both by growing to a size where they put pressure on other tissues and by spreading to other organs.
The functioning, mainly benign islet cell tumors secrete active agents that have characteristic metabolic effects that create more symptoms than the tumor itself. When a functioning tumor becomes extremely large or metastatic, it will cause the same types of signs and symptoms as any other malignant tumor, as well as the hormonal symptoms.
• Gastrinomas (Zollinger-Ellison syndrome) produce an excess amount of gastrin leading to increased
production of stomach acid, severe peptic ulcer disease (multiple ulcers in unusual locations such as the
jejunum) and often severe diarrhea. This syndrome accounts for less than 1 percent of all people with peptic
ulcers. Other symptoms include abdominal pain and extreme weight loss.
• Insulinomas secrete excess insulin, leading to low blood sugar (hypoglycemia). Often, the symptoms of
weight loss, fatigue, weakness and hunger are attributed to psychological or neurologic disorders. Symptoms
may be worse during fasting.
• The overproduction of glucagon by glucagonomas causes a characteristic skin rash (necrolytic migratory
erythema) and a painful tongue (glossitis). Blood clots in the legs, which may travel to the lungs, have also
