Insulin

Insulin is a peptide hormone produced by the β cells of the islets of Langerhans, which are clusters of cells embedded in the endocrine portion of the pancreas (Fig. 1). [Note: “Insulin” is from the Latin for island.] The islets make up only about 1%–2% of the total cells of the pancreas. Insulin is the most important hormone coordinating the use of fuels by tissues. Its metabolic effects are anabolic, favoring, for example, synthesis of glycogen, triacylglycerol (TAG), and protein.

Figure 1:  Islets of Langerhans.