Which of the following does NOT occur when antidiuretic hormone (ADH) is present?

• A. Decreased urine volume
• B. Increased water reabsorption in the kidneys
• C. Dilution of blood plasma
• D. Increased urine osmolarity

Answer: (D)

Verified step by step guidance

1. Understand the role of antidiuretic hormone (ADH): ADH is a hormone that helps regulate water balance in the body by increasing water reabsorption in the kidneys, which reduces urine volume and increases urine osmolarity.
2. Analyze the options provided: Each option describes a physiological effect that could occur when ADH is present. You need to identify the one that does NOT occur.
3. Evaluate 'Decreased urine volume': When ADH is present, water is reabsorbed into the bloodstream, leading to a decrease in urine volume. This is consistent with the function of ADH.
4. Evaluate 'Increased water reabsorption in the kidneys': ADH directly stimulates the kidneys to reabsorb more water, so this is a correct effect of ADH.
5. Evaluate 'Dilution of blood plasma': When ADH is present, water is retained in the bloodstream, which can concentrate the blood plasma rather than diluting it. This does NOT align with the effects of ADH, making it the correct answer.