A patient has abnormally low secretion of antidiuretic hormone but normal kidney function. Which of the following changes in the patient's urine is most likely?
Select one answer.
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Answer: B (Increased urine volume and decreased urine osmolarity)
Antidiuretic hormone increases the permeability of the collecting ducts to water, promoting water reabsorption into the blood. Abnormally low secretion of this hormone therefore reduces water reabsorption and produces a larger volume of more dilute urine. Thus, urine volume increases and urine osmolarity decreases. Choice A describes the effects of increased antidiuretic hormone activity. Choice C incorrectly predicts decreased urine volume, and choice D incorrectly predicts that reduced water reabsorption would concentrate the urine.