Which hormone is released in response to osmolality changes and acts on the kidneys to conserve water?

Which hormone is released in response to osmolality changes and acts on the kidneys to conserve water?

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

Answer: (A)

When plasma osmolality changes, the body uses a hormone to conserve water. Osmoreceptors in the hypothalamus sense that osmolality is rising and trigger the release of antidiuretic hormone (ADH, also known as vasopressin) from the posterior pituitary. ADH travels to the kidneys and binds to V2 receptors on collecting duct cells, activating a signaling cascade that inserts aquaporin-2 water channels into the apical membrane. This increases water permeability, so more water is reabsorbed from the filtrate back into the bloodstream, concentrating the urine and lowering plasma osmolality toward normal. Among the options, this hormone is the primary one that responds directly to osmolality changes to conserve water. Aldosterone mainly adjusts Na+ reabsorption and volume via the RAAS, not driven by osmolality changes. ANP promotes water and sodium excretion in response to stretch from increased volume, and renin is an enzyme that initiates the RAAS rather than directly conserving water in response to osmolality.

When plasma osmolality changes, the body uses a hormone to conserve water. Osmoreceptors in the hypothalamus sense that osmolality is rising and trigger the release of antidiuretic hormone (ADH, also known as vasopressin) from the posterior pituitary. ADH travels to the kidneys and binds to V2 receptors on collecting duct cells, activating a signaling cascade that inserts aquaporin-2 water channels into the apical membrane. This increases water permeability, so more water is reabsorbed from the filtrate back into the bloodstream, concentrating the urine and lowering plasma osmolality toward normal. Among the options, this hormone is the primary one that responds directly to osmolality changes to conserve water. Aldosterone mainly adjusts Na+ reabsorption and volume via the RAAS, not driven by osmolality changes. ANP promotes water and sodium excretion in response to stretch from increased volume, and renin is an enzyme that initiates the RAAS rather than directly conserving water in response to osmolality.