Insulin is a hormone produced by the pancreas. The purpose of insulin is to keep the level of sugar in the blood down to normal levels.
If the level of sugar in the blood begins to rise above certain limits, the Islets of Langerhans respond by releasing insulin in to the bloodstream. The insulin then acts to oppose the effects of hormones such as cortisone and adrenalin, both of which raise the level of sugar in the blood. The insulin exerts its effect by allowing sugar to pass from the bloodstream into the body’s cells to be used as a duel.