The islets of Langerhans are clusters of endocrine tissue found throughout the pancreas that secrete insulin and other hormones.
Insulin is a hormone that allows the body to use and store sugar (glucose) from carbohydrates in food.
Type 1 diabetes mellitus, is caused by the under-activity of the islets of Langerhans causing a lack of insulin. Type 2 diabetes mellitus is a result of the resistance of body cells to use insulin and not from the under-activity of the islets of Langerhans.
Islets of Langerhans were named after German pathologist Paul Langerhans in 1869 who was the first to describe them.