If a marathon runner only consumes electrolyte-free water during a race, which consequence follows regarding plasma osmolality and ADH secretion?

💡 Explanation

If a runner only drinks water, plasma osmolality decreases due to dilution. Because osmoreceptors in the hypothalamus detect this decrease, ADH secretion from the posterior pituitary decreases; therefore, less water is reabsorbed in the kidneys, rather than more being retained, which would occur if ADH increased.

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