What is being tested?Trypsin and chymotrypsin are proteolytic enzymes. Their job is to digest
protein in the small intestine. Normally, their precursors (their inactive forms: trypsinogen and chymotrypsinogen) are produced in the pancreas and transported to the small intestine. In the small intestine, trypsinogen is activated, turned into trypsin, by an enzyme in the intestinal mucosa and then trypsin in turn activates chymotrypsinogen to chymotrypsin. Together, they form powerful chemicals responsible for breaking down the protein in food into smaller pieces called peptides. Trypsin and chymotrypsin will be detectable in the small intestine and in the stool if the pancreas is functioning normally.
In people with cystic fibrosis, mucous plugs can block the pancreatic ducts that lead into the small intestine, preventing trypsinogen and chymotrypsinogen from reaching the intestine. These mucous plugs can also block small airway passages in the lungs, making one susceptible to respiratory infections and chronic pulmonary disease. It is usually the respiratory complications of cystic fibrosis that eventually prove fatal for patients with this disease.
In individuals with pancreatic dysfunction (tissue damage or blockage), there may be either blocked pancreatic ducts or the cells that produce trypsinogen and chymotrypsinogen may be damaged or destroyed. This is often seen in conditions such as chronic pancreatitis and pancreatic cancer; such cell damage causes pancreatic insufficiency, in which not enough of the enzymes reach the small intestine to digest food properly.
