Glucose circulates in the bloodstream and carries energy into the body's cells. But the glucose molecules can't permeate most cells unless a "gatekeeper" hormone, insulin, is present to allow the sugar in. The insulin is produced by a gland—the pancreas—and the amount of insulin released into the bloodstream is regulated by the amount of sugar the pancreas detects in the blood: The more sugar detected, the more insulin released. The two forms of diabetes represent two different derailments of this system; both result in excessive concentrations of sugar in the blood.