Which hormone is secreted by the posterior pituitary and promotes water reabsorption in the kidneys?

Which hormone is secreted by the posterior pituitary and promotes water reabsorption in the kidneys?

• A. Oxytocin
• B. Prolactin
• C. Antidiuretic hormone
• D. Corticotropin

Answer: (C)

Antidiuretic hormone, released by the posterior pituitary, promotes water reabsorption in the kidneys. It acts on the collecting ducts to increase their permeability to water by promoting the insertion of aquaporin-2 channels, so more water is reabsorbed back into the bloodstream. This concentrates the urine and helps maintain blood volume when osmolality is high or volume is low. Oxytocin also comes from the posterior pituitary but drives milk ejection and uterine contractions; prolactin and corticotropin are from the anterior pituitary and don’t control renal water reabsorption.

Antidiuretic hormone, released by the posterior pituitary, promotes water reabsorption in the kidneys. It acts on the collecting ducts to increase their permeability to water by promoting the insertion of aquaporin-2 channels, so more water is reabsorbed back into the bloodstream. This concentrates the urine and helps maintain blood volume when osmolality is high or volume is low. Oxytocin also comes from the posterior pituitary but drives milk ejection and uterine contractions; prolactin and corticotropin are from the anterior pituitary and don’t control renal water reabsorption.