The major target organ for glucagon is the liver.
Glucagon, a hormone secreted by the alpha cells of the pancreas, plays a pivotal role in regulating blood glucose levels. While glucagon is known to influence energy storage in different types of tissues, particularly in response to feeding, its most significant impact and primary site of action for glucose regulation is the liver.
The Liver: Glucagon's Primary Site of Action
In situations where blood glucose levels fall too low (hypoglycemia), glucagon acts predominantly on the liver to elevate glucose levels in the bloodstream. This action is crucial for ensuring that vital organs, especially the brain, receive a continuous supply of energy. The key mechanisms through which glucagon achieves this in the liver include:
- Glycogenolysis: Glucagon stimulates the rapid breakdown of glycogen, which is the stored form of glucose in the liver. This process releases glucose into the bloodstream, providing an immediate increase in blood sugar.
- Gluconeogenesis: It also promotes the synthesis of new glucose from non-carbohydrate sources, such as amino acids and glycerol, within the liver. This pathway ensures a more sustained supply of glucose during prolonged periods of low blood sugar, such as during fasting.
By orchestrating these metabolic processes, glucagon effectively counteracts the effects of insulin, working to raise blood glucose and maintain metabolic balance.
