ABSTRACT
This chapter examines the main physiological actions of insulin, discusses the inverse relationship between circulating glucose and insulin, and presents a brief account of the mechanism of action of insulin. It explores the distinction between type 1 and type 2 diabetes, their aetiology, symptoms, complications and treatment. Insulin is an endocrine hormone, that is, secreted directly into the bloodstream from the hormone-producing endocrine cells of the pancreas. Exocrine secretions are via ducts from the glands, for example, secretion of pancreatic digestive juices via the pancreatic duct into the duodenum. Insulin is an anabolic hormone, that is, it promotes the elaboration of polymers from simpler molecules for the storage of energy resources and for the building up of tissues, for example, muscle. Insulin promotes removal of glucose from the circulation. Two molecules of insulin bind to a subunit on the extracellular domain of the membrane insulin receptor.
