An athlete collapses during a marathon due to severe dehydration. Which mechanism primarily causes decreased urine production in this condition?

💡 Explanation

Dehydration increases plasma osmolality, stimulating the release of antidiuretic hormone (ADH). Because ADH increases water reabsorption in the collecting ducts of the kidneys, less water is excreted as urine; therefore, the athlete's urine production decreases, rather than increasing glomerular filtration or the action of natriuretic peptides.

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