How does the thirst mechanism prevent hypernatremia?

Updated: Dec 22, 2020
  • Author: Ivo Lukitsch, MD; Chief Editor: Vecihi Batuman, MD, FASN  more...
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Answer

Thirst is the body’s mechanism to increase water consumption in response to detected deficits in body fluid. As with AVP secretion, thirst is mediated by an increase in effective plasma osmolality of only 2-3%. Thirst is thought to be mediated by osmoreceptors located in the anteroventral hypothalamus. The osmotic thirst threshold averages approximately 288-295 mOsm/kg. This mechanism is so effective that even in pathologic states in which patients are unable to concentrate their urine (diabetes insipidus) and excrete excessive amounts of urine (10-15 L/d), hypernatremia does not develop because thirst is stimulated and body fluid osmolality is maintained at the expense of profound secondary polydipsia.


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