What is the main function of glucagon in the body?

Glucagon plays a crucial role in the regulation of blood glucose levels, primarily through its action of increasing blood glucose concentrations. It is a hormone produced by the alpha cells of the pancreas and acts when blood glucose levels are low, such as during fasting or intense physical activity.

When glucagon is secreted, it stimulates the liver to convert stored glycogen into glucose in a process known as glycogenolysis. Additionally, it promotes gluconeogenesis, which is the process of producing glucose from non-carbohydrate sources. The overall effect of glucagon is to raise blood glucose levels, ensuring that the body has adequate energy, especially for vital functions and maintaining homeostasis. This action is especially important in maintaining glucose availability for organs that rely heavily on it, such as the brain.

The other choices relate to functions that do not accurately represent glucagon's primary role. For example, while some hormones are involved in calcium regulation or stimulate insulin production, glucagon’s primary and most significant function is specifically to increase blood glucose levels.