Incretins are hormones released from the gut in response to nutrient ingestion that potentiate glucose-stimulated insulin secretion. The search for incretins was prompted by the observation that administration of an oral glucose load leads to a much greater stimulation of insulin response than that obtained when glucose is infused intravenously to give identical blood glucose levels . This difference between the two ways of glucose administration has been attributed to incretin hormones, glucagon-like peptide-1 (GLP-1) and glucose- dependant insulinotropic polypeptide (GIP), involved in the...