Pancreatic Hormones and Glucose Regulation

The pancreatic islets continuously balance two opposing hormones: insulin and glucagon. Their shared task is to keep enough glucose circulating for the brain and other tissues without allowing glucose to remain excessively high after eating. Beta cells release insulin when blood glucose rises. Insulin promotes glucose uptake into insulin-responsive tissues and tells the liver to reduce glucose output. This hepatic effect matters because the liver is not simply a storage site; it can release glucose into the circulation between meals. Insulin restrains that release. Alpha cells release glucagon when blood glucose falls. Glucagon tells the liver to break down stored glycogen and make new glucose through gluconeogenesis. During fasting, this prevents blood glucose from falling too far. After a meal, insulin should predominate: glucose moves from the bloodstream into cells, and hepatic glucose production decreases. Between meals, glucagon becomes more influential, maintaining a usable circulating glucose level. Disease develops when this balance fails.