(gloo'kă-gŏn )

A polypeptide hormone secreted by the alpha cells of the pancreas that increases the blood glucose level by stimulating the liver to change stored glycogen to glucose. Glucagon opposes the action of insulin and can be used in an injection to reverse severe hypoglycemia, particularly when a patient has lost consciousness. Parenteral administration of glucagon also relaxes the smooth muscle of the stomach, duodenum, small bowel, and colon.

Glucagon should not be administered to people with pheochromocytoma.