Glucagon
Say it: GLOO-kuh-gon
Glucagon is a peptide hormone made by alpha cells of the pancreas that raises blood glucose, mainly by making the liver release glucose.
Definition
What is glucagon?
Glucagon is a peptide hormone secreted by the alpha cells of the pancreatic islets. It is released when blood glucose falls, for example between meals, during fasting or during long periods of exercise, and its job is the reverse of insulin's: to bring blood glucose back up.
Glucagon acts mainly on the liver. It triggers glycogenolysis, the breakdown of stored glycogen into glucose, and gluconeogenesis, the making of new glucose from amino acids and other small molecules. It also promotes the breakdown of stored fat into fatty acids and glycerol, which gives tissues another fuel and the liver more raw material for making glucose. As blood glucose climbs again, glucagon release falls and insulin release rises. This push and pull between two hormones with opposite effects is a textbook example of antagonistic hormones and of negative feedback in homeostasis.
Glucagon is also used as a medicine. An injection is given as emergency treatment for severe hypoglycemia, dangerously low blood sugar, in people with diabetes, and it is sometimes used during X-ray examinations to relax the muscles of the digestive tract.
Word parts
Where does the word “glucagon” come from?
- gluc-
- sweet; from glucoseGreek glykys
- -agon
- leading, drivingGreek agein
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Terms that go with it
- InsulinInsulin is a peptide hormone made by beta cells in the pancreas that lowers blood glucose by helping body cells take up and store sugar.
- PancreasThe pancreas is a gland behind the stomach that sends digestive enzymes to the small intestine and releases insulin and glucagon into the blood.
- LiverThe liver is the largest gland and internal organ, lying in the upper right abdomen, where it makes bile, processes nutrients and clears toxins.
- HormoneA hormone is a chemical messenger released into the blood by a gland or cell that changes the activity of distant target cells with matching receptors.
- HomeostasisHomeostasis is the body's ability to keep internal conditions, such as temperature, blood glucose and pH, steady while conditions around it change.
- Diabetes mellitusDiabetes mellitus is a chronic disease in which blood glucose stays too high because the body makes too little insulin or cannot use it well.
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