Which organ in the human body produces insulin?

The pancreas sits behind the stomach and does two very different jobs at once. Most of its bulk is devoted to digestion, secreting enzymes into the small intestine that break down fats, proteins and starches. Scattered through that tissue are small islands of hormone-producing cells, the islets of Langerhans, named after the medical student who first described them. Within the islets, beta cells release insulin when blood sugar rises after a meal, telling muscle, fat and liver cells to take glucose out of the bloodstream and store it. Alpha cells release glucagon, which does the opposite and pushes stored glucose back out when levels drop, so the two hormones work as a balancing pair. In type 1 diabetes the immune system destroys the beta cells and insulin must be supplied by injection. In type 2 the cells still make insulin but the body responds to it poorly, a condition called insulin resistance.

Insulin was first isolated in Toronto in the early 1920s, turning type 1 diabetes from a fatal illness into a manageable one.