Which hormone raises blood glucose levels?

• A. Glucagon
• B. Insulin
• C. Somatostatin
• D. Estrogen

Answer: (A)

Glucagon raises blood glucose by triggering hepatic glucose production. When blood glucose falls, pancreatic alpha cells release glucagon, which binds to receptors on liver cells and activates a cAMP signaling cascade. This promotes glycogenolysis (breaking down glycogen into glucose) and gluconeogenesis (producing glucose from non-carbohydrate sources). It also increases the activity of enzymes like glucose-6-phosphatase, helping release glucose into the bloodstream. The net effect is higher blood glucose, especially during fasting or between meals. Insulin does the opposite by promoting glucose uptake and storage; somatostatin mainly modulates other hormones, and estrogen is not a primary regulator of acute glucose levels.