What is the role of glucagon in glucose regulation and when is it used clinically?

• A. Glucagon decreases hepatic glucose production and is used for hyperglycemia.
• B. Glucagon has no role in glucose regulation.
• C. Glucagon raises blood glucose by stimulating hepatic glycogenolysis; used in severe hypoglycemia if IV glucose not available or patient cannot swallow.
• D. Glucagon directly stimulates insulin secretion.

Answer: (C)

Glucagon’s job is to raise blood glucose when levels are low. It acts on the liver, binding to glucagon receptors and triggering a cascade that increases cAMP. This activates enzymes that promote glycogenolysis (breaking down glycogen into glucose) and supports gluconeogenesis (making new glucose). The result is a rapid increase in hepatic glucose output, which helps correct hypoglycemia.

Clinically, glucagon is used in severe hypoglycemia when intravenous glucose isn’t available or the patient cannot swallow. It’s given by intramuscular or subcutaneous injection and typically acts within minutes. Its effectiveness depends on having usable liver glycogen stores; if those stores are depleted, the response may be limited. It does not treat hyperglycemia, and it does not directly stimulate insulin secretion.