Which hormone from the adrenal gland initiates the fight-or-flight response?

• A. Epinephrine
• B. Cortisol
• C. Progesterone
• D. Calcitonin

Answer: (A)

The fight-or-flight response is triggered by a rapid hormonal signal from the adrenal medulla when the sympathetic nervous system is activated. The hormone released is epinephrine (adrenaline). It acts quickly to prepare the body: increasing heart rate and force of contraction, opening airways, raising blood glucose by stimulating glycogen breakdown, and redirecting blood toward muscles. Cortisol, while also a stress hormone, comes from the adrenal cortex and acts more slowly to mobilize energy over minutes to hours rather than initiating the immediate response. Progesterone and calcitonin do not drive this rapid reaction—progesterone is a reproductive hormone, and calcitonin helps regulate calcium.