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MCAT Biology Question — ADH Hormone

Antidiuretic hormone (ADH) is responsible for the retention of water in the body. In the kidney, ADH increases reabsorption at the collecting duct. Which of the following physiological responses will be most likely in a patient suffering from severe dehydration?


  1. Decreased secretion of ADH resulting in decreased blood volume
  2. Increased secretion of ADH resulting in decreased blood volume
  3. Decreased secretion of ADH resulting in increased blood volume
  4. Increased secretion of ADH resulting in increased blood volume
Click for Explanation

This question is asking you to determine the body’s hormonal response with respect to ADH in the case of a person suffering from dehydration. Dehydration is the result of a low blood volume, which leads to low blood pressure. To maintain homeostasis, the body will attempt to equilibrate by increasing blood volume, which in turn, increases blood pressure. Since ADH increases reabsorption of water from the filtrate to the bloodstream, the body is expected to secrete high levels of antidiuretic hormone, which will cause an increase in blood volume. Thus the correct answer is D.

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