A protein hormone secreted by pancreatic endocrine cells that raises blood glucose levels and is antagonistic to insulin is called what?

• A. Insulin
• B. Cortisol
• C. Glucagon
• D. Epinephrine

Answer: (C)

Glucagon is the peptide hormone released by pancreatic alpha cells. Its primary role is to raise blood glucose when levels are low, mainly by signaling the liver to break down glycogen (glycogenolysis) and to generate new glucose from non-carbohydrate sources (gluconeogenesis), increasing glucose release into the bloodstream. It acts in opposition to insulin, which lowers blood glucose by promoting uptake and storage of glucose. The other options don’t fit because insulin lowers glucose and comes from pancreatic beta cells, cortisol is a steroid produced by the adrenal cortex, and epinephrine is a catecholamine from the adrenal medulla.