Which hormone is secreted by the posterior pituitary gland and causes the kidneys to reabsorb water and is a potent vasoconstrictor?

Which hormone is secreted by the posterior pituitary gland and causes the kidneys to reabsorb water and is a potent vasoconstrictor?

• A. ADH
• B. PTH
• C. TSH
• D. DH

Answer: (A)

Antidiuretic hormone, also called vasopressin, is released by the posterior pituitary and has two key actions that match the prompt. In the kidneys, it binds to V2 receptors on the collecting duct cells, triggering a cascade that inserts aquaporin-2 water channels into the apical membrane. This makes the ducts more permeable to water, so more water is reabsorbed back into the bloodstream, urine becomes more concentrated, and urine output decreases. Simultaneously, ADH acts on vascular smooth muscle via V1 receptors to cause vasoconstriction, raising systemic vascular resistance and blood pressure—hence its description as a potent vasoconstrictor. PTH, TSH, and any nonstandard term like DH don’t cause water reabsorption in the kidneys or function as a strong vasoconstrictor, so they don’t fit the prompt.

Antidiuretic hormone, also called vasopressin, is released by the posterior pituitary and has two key actions that match the prompt. In the kidneys, it binds to V2 receptors on the collecting duct cells, triggering a cascade that inserts aquaporin-2 water channels into the apical membrane. This makes the ducts more permeable to water, so more water is reabsorbed back into the bloodstream, urine becomes more concentrated, and urine output decreases.

Simultaneously, ADH acts on vascular smooth muscle via V1 receptors to cause vasoconstriction, raising systemic vascular resistance and blood pressure—hence its description as a potent vasoconstrictor.

PTH, TSH, and any nonstandard term like DH don’t cause water reabsorption in the kidneys or function as a strong vasoconstrictor, so they don’t fit the prompt.