Insulin-A protein hormone liberated by the beta cells of the pancreas. Liberation of insulin from the pancreas is stimulated by the consumption of glucose and certain dietary proteins. Once glucose is absorbed from the Gastrointestinal tract and passes into the blood, the elevated levels of glucose act as a stimulus for the pancreas to secrete insulin into the blood. Insulin then functions by facilitating the storage and optimum usage of these "energy-containing" molecules. Insulin promotes the passage of glucose into cells that can store this sugar as either carbohydrates (storage form of sugars) or fats (another energy storage).