Insulin (from Latin insula, “island”, as it is produced in the Islets of Langerhans in the pancreas) is an anabolic polypeptide hormone that reregulates blood plasma glucose levels and the availability and entry of macronutrients to the cellular mitochondria. Insulin is composed of 51 amino acid residues and has a molecular weight of 5808. Insulin’s structure varies slightly between animal species. Apart from being the primary agent in carbohydrate homeostasis, it has effects on amino acid & fat metabolism as well as changes the liver’s activity in storing or releasing glucose and in processing blood lipids. Insulin exerts a strong effect on other tissues such as fat and muscle. The amount of insulin in circulation has extremely widespread effects throughout the body.