Insulin is a hormone that regulates the amount of glucose (sugar) in the blood and is required for the body to function normally. Insulin is produced by cells in the pancreas, called the islets of Langerhans. These cells continuously release a small amount of insulin into the body, but they release surges of the hormone in response to a rise in the blood glucose level. The major use of producing insulin is for diabetics who do not make enough or any insulin naturally. Human insulin is grown in the lab inside common bacteria. Escherichia coli is by far the most widely used type of bacterium, but yeast is also used. Researchers need the human protein that produces insulin. Manufacturers get this through an amino-acid sequencing machine that synthesizes the DNA.