Which organ produces the hormone insulin in the human body?

The pancreas produces the hormone insulin in the human body.

Insulin is made by beta cells in clusters called the islets of Langerhans. After a meal, rising blood glucose stimulates insulin release. Insulin helps cells take up glucose and encourages the liver and muscles to store glucose as glycogen, helping regulate the amount of sugar in the bloodstream.

The pancreas has both endocrine and exocrine functions. Its endocrine cells release hormones directly into the blood, while its exocrine tissue sends digestive enzymes through ducts into the small intestine. Glucagon, made mainly by alpha cells in the pancreatic islets, generally raises blood glucose and works in opposition to insulin. Diabetes mellitus can result when insulin production is insufficient, insulin action is impaired, or both. Insulin was first successfully used as a treatment for diabetes in 1922 after pioneering work in Toronto.