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Definition of INSULIN
: a protein pancreatic hormone secreted by the beta cells of the islets of Langerhans that is essential especially for the metabolism of carbohydrates and the regulation of glucose levels in the blood and that when insufficiently produced results in diabetes mellitus
New Latin insula islet (of Langerhans), from Latin, island
First Known Use: 1914
Medical Definition of INSULIN
: a protein hormone that is synthesized in the pancreas from proinsulin and secreted by the beta cells of the islets of Langerhans, that is essential for the metabolism of carbohydrates, lipids, and proteins, that regulates blood sugar levels by facilitating the uptake of glucose into tissues, by promoting its conversion into glycogen, fatty acids, and triglycerides, and by reducing the release of glucose from the liver, and that when produced in insufficient quantities results in diabetes mellitus—see iletin
Polypeptide hormone (seepeptide) that regulates blood glucose levels. Secreted by the islets of Langerhans (seeLangerhans, islets of) in the pancreas when blood glucose rises, as after a meal, it helps transfer the glucose into the body's cells to be oxidized (seeoxidation-reduction) for energy or converted and stored as fatty acids or glycogen. When blood glucose falls, insulin secretion stops and the liver releases more glucose into the blood. Insulin has various related functions in the liver, muscles, and other tissues, controlling the balance of glucose with related compounds. Insulin-related disorders include diabetes mellitus and hypoglycemia. Frederick Banting and J.J.R. Macleod won a Nobel Prize in 1923 for discovering insulin, and Frederick Sanger won one in 1958 for determining its amino acid sequence.