Which hormone decreases blood sugar?

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

Answer: (A)

When blood glucose is high, a hormone released by the pancreas triggers the uptake and storage of glucose, lowering the level in the blood. This hormone promotes glucose entry into muscle and fat cells by moving GLUT4 transporters to the cell surface, stimulates the liver to store glucose as glycogen, and enhances glycolysis while inhibiting glucose production by the liver. In short, it shifts glucose from the bloodstream into tissues and stores, which reduces blood sugar.

The other hormones tend to raise blood sugar: glucagon promotes glycogen breakdown and glucose production in the liver; epinephrine stimulates glycogenolysis and fat breakdown to provide quick energy; cortisol increases glucose production through gluconeogenesis and can reduce glucose uptake in some tissues.