islet of Langerhans

islet of Langerhans A group of specialized cells in the pancreas that make and secrete hormones, including insulin. These cells sit in groups (islets), with several different types of cells in an islet, including alpha cells that make glucagon, which raises the level of glucose (sugar) in the blood; beta cells that make insulin; and delta cells that make somatostatin, which inhibits the release of numerous other hormones in the body. Degeneration of the insulin-producing beta cells is the main cause of type 1 (insulin-dependent) diabetes mellitus.