What is the primary function of glucagon?

Glucagon primarily functions to increase blood sugar levels, which is crucial for maintaining energy homeostasis in the body. It is a hormone produced by the alpha cells of the pancreas and plays a key role during fasting or low blood glucose conditions. When blood sugar levels drop, glucagon prompts the liver to convert stored glycogen into glucose through a process known as glycogenolysis and also encourages gluconeogenesis, where the liver generates glucose from non-carbohydrate sources.

This action serves to elevate blood glucose levels, ensuring that the body has a continuous energy supply, especially for organs that rely heavily on glucose, like the brain. The regulation of blood sugar is particularly vital for individuals with diabetes or related metabolic disorders, where the body's normal response mechanisms may be impaired.

While the other choices relate to metabolic processes, they do not align with the primary function of glucagon. Decreasing blood sugar levels is the job of insulin, while fat metabolism regulation and bile production are not direct effects of glucagon. Thus, the elevation of blood sugar levels by glucagon stands out as its main role in body metabolism.