Why does diabetes insipidus often result in increased serum osmolality and dehydration?

💡 Explanation

Diabetes insipidus leads to insufficient or ineffective ADH. The reduced ADH impairs the countercurrent multiplier system within the renal collecting ducts, which normally enhances water reabsorption; therefore, water is lost in urine rather than being reabsorbed, because of impaired water reabsorption, leading to dehydration and increased serum osmolality, rather than ADH increasing water reabsorption.

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