Which hormone is released by the posterior pituitary during the alarm stage?

• A. ADH
• B. ACTH
• C. Cortisol
• D. Epinephrine

Answer: (A)

During the alarm stage of the stress response, the body activates systems to preserve volume and pressure. The posterior pituitary releases vasopressin, also known as antidiuretic hormone. ADH acts on the kidneys to increase water reabsorption in the collecting ducts, which helps maintain circulating blood volume and blood pressure when stress is detected. This rapid hormonal response complements the sympathetic surge that releases epinephrine from the adrenal medulla, but the hormone coming from the posterior pituitary is ADH. The other hormones listed come from different glands: ACTH from the anterior pituitary stimulates the adrenal cortex to release cortisol, and epinephrine is produced by the adrenal medulla in response to sympathetic activation.