Which organ produces the hormone insulin?

The organ that produces the hormone insulin is the pancreas. Specialized clusters of endocrine cells called the islets of Langerhans contain beta cells, which make and release insulin into the bloodstream.

Insulin helps the body control blood glucose. After a meal, rising blood sugar stimulates pancreatic beta cells to secrete insulin. The hormone encourages cells in the liver, skeletal muscles, and fat tissue to take up glucose, while also promoting storage of excess glucose as glycogen and reducing the liver’s glucose production.

The pancreas has two major roles. Its endocrine function releases hormones such as insulin, glucagon, and somatostatin into the blood. Its exocrine function sends digestive enzymes through ducts into the small intestine, where they help break down carbohydrates, proteins, and fats.

A common mix-up is assuming the liver produces insulin because the liver is central to blood-sugar regulation. The liver stores and releases glucose and responds strongly to insulin, but pancreatic beta cells produce the hormone. In type 1 diabetes, immune destruction of these cells causes severe insulin deficiency; type 2 diabetes usually involves insulin resistance combined with declining beta-cell function.