What hormone causes the liver to release glycogen?

The hormone that causes the liver to release glycogen is glucagon. Glucagon is secreted by the alpha cells of the pancreas when blood glucose levels are low. Its primary function is to raise blood glucose levels by stimulating the liver to convert stored glycogen into glucose, a process known as glycogenolysis. This release provides an immediate source of glucose that can be used for energy by the body's cells.

In contrast, insulin, which promotes the storage of glucose as glycogen, works to lower blood glucose levels and is primarily active after food intake. Aldosterone is involved in regulating sodium and potassium levels, not in glucose metabolism. Epinephrine, while it can influence glucose levels by stimulating glycogenolysis, acts more broadly in response to stress and is not the primary hormone responsible for initiating this process in typical scenarios. Thus, glucagon is the key hormone for glycogen release from the liver.