What is the main function of glucagon in the body?

Glucagon plays a critical role in regulating blood glucose levels, primarily by increasing them when they fall too low. It is a hormone produced by the alpha cells of the pancreas. When blood sugar levels decrease, glucagon is secreted into the bloodstream and acts primarily on the liver. There, it stimulates glycogenolysis, the process by which glycogen is broken down into glucose, and gluconeogenesis, where new glucose is created from non-carbohydrate sources. This release of glucose into the bloodstream raises blood sugar levels, providing essential energy to the body's cells, particularly during fasting or between meals.

In contrast to other hormones like insulin, which lowers blood glucose levels, glucagon's main function ensures that glucose is available for energy production, particularly during periods of low energy intake or increased energy demand. This balance is vital for maintaining homeostasis in the body.