Cholecystokinin (CCK) is a hormone produced by the cells in the small intestine, particularly in response to the presence of fats and proteins in food. Its primary role is to stimulate the gallbladder to release bile, which helps in the digestion of fats. CCK also signals the pancreas to release digestive enzymes, aiding in the breakdown of food. In addition to its digestive functions, CCK plays a role in regulating appetite. It helps promote a feeling of fullness after eating, which can influence food intake. This hormone is an important part of the complex system that manages digestion and hunger in the body.