The metabolism of carbohydrates is regulated by a variety of hormones and other molecules.
Insulin: Insulin is a polypeptide, is secreted from the pancreas in response to a hyperglycemia condition which usually results shortly after ingesting a meal. The major effect of insulin is to promote the transport of sugar across the cell membrane of fat and muscle cells. In addition, insulin promotes anabolic processes such as increasing the rate of synthesis for glycogen, fatty acids, and proteins. Insulin inhibits the catabolic processes such as the breakdown of glycogen and fat. A deficiency of insulin (hyperinsulinism) results in a permanent hyperglycemic condition known as diabetes mellitus.
Glucagon: If one hormone, insulin, controls the excess of glucose in the blood by stimulating the synthesis of glycogen, then other hormones must respond to low levels of glucose. The liver is more responsive to glucagon a peptide also secreted by the pancreas. Glucagon increases glucose levels in the blood by stimulating the breakdown of glycogen in the liver into glucose which leaves the liver cells and enters the bloodstream.