Revision 6 for 'Glucagon'

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Glucagon is a polypeptide hormone central to the regulation of glucose homeostasis, acting as an antagonist to insulin. In imaging it has been used as an adjunct agent in nuclear medicine studies

Structure and mechanism of action

Glucagon is a 29 amino acid polypeptide hormone that is enzymatically-derived from proglucagon, its biochemical precursor. Glucagon acts via a G protein-coupled transmembrane receptor.

Glucagon is secreted from the 

Glucose regulation

Glucose homeostasis is extremely complex.  The main action of glucagon is hyperglycemic, achieved through gluconeogenesis and glycogenolysis. Fundamentally it ensures that the supply of glucose to the brain is maintained 1.

Insulin, gamma-aminobutyric acid (GABA) and leptin are the main actors in inhibiting glucagon secretion. 


Hyperglucagonemia has been found in all cases of diabetes mellitus, therefore glucagon has become a major target for the pharmaceutical industry in the development of new diabetic medications 1.

In the rare tumor glucagonoma, the hypersecretion of glucagon leads to its clinical presentation. 



History and etymology

Unusually glucagon was named before it was discovered! 
In 1922 Banting et al. found that crude pancreatic extracts given to children with diabetes produced a short-lived elevation of the serum glucose before insulin's desired hypoglycemic effect. It was postulated that an unknown substance, named glucagon, was responsible 3. It was only in 1955 that the polypeptide responsible was finally purified 1.

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