The hormones that stimulate the breakdown of liver glycogen are epinephrine and glucagon. Epinephrine is the one that triggers the glycogen breakdown inside the muscle and also inside the liver. However, the liver is the one that is more active or responsive to the hormone called glucagon than the muscles. A glucagon is a hormone which is a polypeptide hidden by the cells of our pancreas called α cells whenever our blood-sugar is low. This hormone indicates the state of starving.