Which hormone causes kidneys to increase water reabsorption?

Which hormone causes kidneys to increase water reabsorption?

• A. Aldosterone
• B. Calcitonin
• C. ADH
• D. Renin

Answer: (C)

Water reabsorption in the kidney is controlled by a hormone that directly increases the permeability of the collecting ducts to water. This hormone, antidiuretic hormone (ADH), is released in response to higher blood osmolality or lower blood volume. It acts on collecting-duct cells to insert aquaporin-2 water channels into their apical membranes, allowing water to be reabsorbed from the filtrate back into the bloodstream. The result is more water reabsorbed and a smaller volume of more concentrated urine. Aldosterone promotes sodium reabsorption (and water follows indirectly), but the direct driver of water permeability is ADH. Calcitonin doesn’t regulate kidney water reabsorption, and renin’s role is in blood pressure and volume regulation indirectly, not in directly increasing water permeability in the collecting ducts.

Water reabsorption in the kidney is controlled by a hormone that directly increases the permeability of the collecting ducts to water. This hormone, antidiuretic hormone (ADH), is released in response to higher blood osmolality or lower blood volume. It acts on collecting-duct cells to insert aquaporin-2 water channels into their apical membranes, allowing water to be reabsorbed from the filtrate back into the bloodstream. The result is more water reabsorbed and a smaller volume of more concentrated urine. Aldosterone promotes sodium reabsorption (and water follows indirectly), but the direct driver of water permeability is ADH. Calcitonin doesn’t regulate kidney water reabsorption, and renin’s role is in blood pressure and volume regulation indirectly, not in directly increasing water permeability in the collecting ducts.