Which hormone raises the level of glucose in the blood by signaling the liver to release glucose?

Which hormone raises the level of glucose in the blood by signaling the liver to release glucose?

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

Answer: (D)

When blood sugar drops, the body uses a hormone signal to raise glucose by telling the liver to release stored sugar. That signal is glucagon, produced by the pancreas. Glucagon binds to receptors on liver cells and activates a cascade that raises cAMP levels, turning on enzymes that break down glycogen (glycogenolysis) and stimulate new glucose production from non-carbohydrate sources (gluconeogenesis). The result is more glucose released into the bloodstream.

Insulin does the opposite, promoting glucose uptake by tissues and storage as glycogen and fat, and reducing glucose production. The other choices, estrogen and testosterone, are sex hormones that influence metabolism more broadly but do not directly signal the liver to release glucose in the way glucagon does.