A hormone released by the duodenum (the first part of the small intestine) in response to the excessive presence of fatty acids in the small intestine. The hormone is only 33 amino acids long, and when released, it causes the release of enzymes from the pancreas and the gall bladder to contract.
From the BioTech Dictionary at http://biotech.icmb.utexas.edu/. For further information see the BioTech homenode.