The pancreas contains isolated groups of endocrine cells known as the islands of Langerhans. The beta cells of these islands produce insulin, a protein hormone that regulates carbohydrate metabolism, specifically the utilization of glucose. Extensive or complete failure of the islands of Langerhans to secrete insulin cause the disease diabetes mellitus, which is characterized by thirst, enhanced appetite, urinary frequency, high blood glucose, weakness, emaciation, and the appearance of sugar in the urine. Obesity and heredity are predisposing factors. In at least a fourth of the case there is a family history of diabetes.

The discovery that insulin can be extracted from the pancreas of animals and that it ensures the proper use of glucose made possible the successful treatment of diabetes. In persons in whom the pancreas produces nearly enough insulin, the condition may be controlled by a modification of the diet.

Drugs that can be taken orally aid some persons with mild diabetes by apparently stimulating the islands of langerhans. If the disease is severe, insulin must be injected regularly. The amount needed is influenced by the amount of carbohydrate in the diet and by the amount of exercise the person takes. Exercise decreases the need for insulin by facilitating the burning of blood sugar.

Some persons develop disturbances caused by the hyperfunctioning of the islands of Langerhans. The physiologic disturbance is hypoglycemia. The condition may result in faintness, dizziness, sweating, and nervourness when the blood sugar level reaches an unduly low point.

Other cells in the islands of langerhans, called alpha cells, produce the hormone glucagon, whose effect on carbohydrate metabolism is opposite to that of insulin. It has the ability to raise blood sugar and is secreted in response to hypoglycemia. Glucagon is used in the emergency treatment of insulin shock.