Which of the following statements about antidiuretic hormone are correct?
I) Antidiuretic hormone acts on the kidneys.
II) Antidiuretic hormone is released in response to high blood solute concentration.
III) Antidiuretic hormone reduces urine output.

• A. I & II.
• B. II & III.
• C. I & III.
• D. I, II, & III.

Answer: (D)

Verified step by step guidance

1. Step 1: Understand the role of antidiuretic hormone (ADH). ADH, also known as vasopressin, is a hormone that helps regulate water balance in the body by acting on the kidneys to promote water reabsorption. This reduces urine output and helps maintain blood pressure and hydration levels.
2. Step 2: Analyze statement I: 'Antidiuretic hormone acts on the kidneys.' This is correct because ADH targets the kidneys, specifically the collecting ducts, to increase water reabsorption.
3. Step 3: Analyze statement II: 'Antidiuretic hormone is released in response to high blood solute concentration.' This is correct because ADH secretion is triggered by an increase in blood osmolality (high solute concentration), which signals the body to conserve water.
4. Step 4: Analyze statement III: 'Antidiuretic hormone reduces urine output.' This is correct because by increasing water reabsorption in the kidneys, ADH decreases the volume of urine produced.
5. Step 5: Combine the analysis of all three statements. Since all three statements (I, II, and III) are correct, the correct answer is 'I, II, & III.'