Insulin

Insulin, hormone, produced in the islets of Langerhans of the pancreas, that regulates the metabolism of carbohydrates, fats, and starches in the body. Insulin enables the cells of the body to take up glucose, the simple sugar that cells burn for energy. If the pancreas does not produce sufficient insulin, or if the cells become resistant to the effects of insulin, the body cannot use glucose effectively, and the disease diabetes mellitus results. This is a serious illness that can lead to kidney failure, blindness, and death if left untreated.

Patients with severe diabetes must take insulin to control their disease. But insulin is a protein, and like other proteins, it is partially digested if administered orally. Hence patients who require insulin have traditionally needed to inject the hormone into a muscle. In 2006, the U.S. Food and Drug Administration approved a form of insulin that is administered by inhaling the drug, which then enters the bloodstream through the lungs.

Insulin was first extracted from the pancreatic tissue of dogs in 1921 by the Canadian physiologists Sir Frederick Grant Banting and Charles Herbert Best and the British physiologist John James Rickard Macleod. The Canadian biochemist James Bertram Collip then produced it in sufficiently pure form to be injected into humans. The molecular structure of insulin was determined in 1955 by the British biochemist Frederick Sanger; it was the first protein to be deciphered. Human insulin, the first human protein to be synthesized, was made in 1965. In 1981 insulin made in bacteria by genetic engineering became the first human hormone obtained in this way to be used to treat human disease. For the biochemistry of insulin, see Sugar Metabolism.