Glucagon is a peptide hormone that is produced and secreted by alpha cells in the pancreas. Its primary function is to regulate blood glucose levels, particularly in times of low blood sugar levels, through a process called gluconeogenesis. During gluconeogenesis, glucagon stimulates the liver to break down stored glycogen into glucose, which is then released into the bloodstream to provide energy for the body. Glucagon also has other functions, such as promoting the breakdown of fats to provide energy and inhibiting glycogen synthesis. Overall, glucagon plays a crucial role in maintaining normal blood sugar levels and energy homeostasis in the body.