Which hormone is responsible for the fight or flight response?

• A. Adrenaline
• B. Insulin
• C. Thyroxine
• D. Progesterone

Answer: (A)

When a sudden threat or stress hits, the body rapidly gears up through adrenaline release from the adrenal medulla as part of the sympathetic nervous system. This hormone acts quickly to prepare for action: it raises heart rate and the force of heart contractions, opens the airways to improve breathing, and redirects blood to muscles so you can move fast. It also stimulates the liver to break down glycogen, increasing blood glucose for immediate energy and sharpening mental alertness. Insulin would actually lower blood glucose and isn’t part of the immediate stress response. Thyroxine boosts metabolic rate but works over a longer timescale, not the rapid surge needed in a fight-or-flight moment. Progesterone governs reproductive processes and doesn’t mediate this acute response. Adrenaline is the key driver of the rapid, whole-body adjustments that enable quick, decisive action.