Glucagon's primary physiological function is to maintain hepatic glucose production, especially during fasting and stress.
Glucagon's Role in Glucose Regulation
Glucagon, secreted into the portal vein, exerts its main effects on the liver. It helps prevent hypoglycemia (low blood sugar) by:
- Glycogen Breakdown: As stated in the reference, glucagon's major action is to break down glycogen in the liver. This process, called glycogenolysis, releases glucose into the bloodstream, raising blood sugar levels.
- Hepatic Glucose Production During Fasting: During periods of fasting, when dietary glucose is unavailable, glucagon stimulates the liver to produce glucose, maintaining a stable blood glucose level.
- Increased Hepatic Glucose Production During Stress: Glucagon also plays a role in increasing glucose production during stressful situations, including hypoglycemia itself. This ensures the body has adequate energy to cope with the stress.
Summary of Glucagon's Physiological Function
| Function | Description | Importance |
|---|---|---|
| Glycogenolysis (Glycogen Breakdown) | Stimulates the liver to break down stored glycogen into glucose. | Quickly raises blood glucose levels when they drop. |
| Hepatic Glucose Production | Increases glucose synthesis by the liver (gluconeogenesis). | Provides a sustained source of glucose during fasting or increased demand. |
| Counterregulation to Insulin | Opposes the actions of insulin, preventing blood glucose from falling too low. | Maintains glucose homeostasis and prevents hypoglycemia. |
In essence, glucagon acts as a counter-regulatory hormone to insulin, preventing blood glucose levels from falling too low and ensuring a constant energy supply for the body, particularly the brain.
