Which condition triggers the release of ADH?

Which condition triggers the release of ADH?

• A. Decreased blood osmolarity
• B. Increased osmolarity/dehydration
• C. Increased plasma volume
• D. Decreased blood pressure

Answer: (B)

The main factor driving ADH release is an increase in plasma osmolality, such as occurs with dehydration. When the blood becomes more concentrated, osmoreceptors in the hypothalamus sense this change and stimulate the posterior pituitary to secrete ADH. ADH then acts on the kidney’s collecting ducts to insert aquaporin-2 channels, increasing water reabsorption. This concentrates the urine and helps restore blood osmolality and stabilize blood pressure. Changes in blood volume or pressure can also influence ADH via baroreceptors, but the most direct trigger is higher osmolarity from dehydration. Lower osmolarity would suppress ADH, and a rise in plasma volume would reduce the need for ADH.

The main factor driving ADH release is an increase in plasma osmolality, such as occurs with dehydration. When the blood becomes more concentrated, osmoreceptors in the hypothalamus sense this change and stimulate the posterior pituitary to secrete ADH. ADH then acts on the kidney’s collecting ducts to insert aquaporin-2 channels, increasing water reabsorption. This concentrates the urine and helps restore blood osmolality and stabilize blood pressure.

Changes in blood volume or pressure can also influence ADH via baroreceptors, but the most direct trigger is higher osmolarity from dehydration. Lower osmolarity would suppress ADH, and a rise in plasma volume would reduce the need for ADH.