Glucagon is a peptide hormone, produced by alpha cells of the pancreas. The pancreas releases glucagon when the concentration of insulin in the bloodstream falls too low. It works to raise the concentration of glucose and fatty acids in the bloodstream, and is considered to be the main catabolic hormone of the body. It is also used as a medication to treat a number of health conditions. Its effect is opposite to that of insulin, which lowers the extracellular glucose.