Although many nonfunctional GI NETs may grow for a long time without causing signs or symptom, some nonfunctional tumors may cause signs or symptoms if the tumor blocks parts of the GI tract.
In functional GI NETs, the hormones released are usually metabolized as the blood flows from the gut to the liver. If the tumor has spread to the liver and the liver enzymes cannot destroy the extra hormones made by the tumor, high amounts of these hormones may remain in the body and cause carcinoid syndrome.
Carcinoid syndrome
The signs and symptoms of carcinoid syndrome include: