Chronic hyponatraemia with a reset osmostat: when abnormal is normal.
Hannah Butaye, Lotte Hoskens, Detlef Bockenhauer
✦ AI-curated · Sources linked
Case in brief
An adolescent was evaluated for chronic hyponatraemia. Assessment of volume status indicated a euvolaemic presentation, prompting consideration of causes beyond salt depletion or excess water. Simple diagnostic tests supported a reset osmostat: regulation of plasma osmolality around a set point below the normal range. The report describes the diagnostic reasoning leading to this diagnosis; the abstract does not provide further clinical findings or a treatment outcome.
What made this case unusual
The diagnostic consideration was a reset osmostat, an often-forgotten explanation for chronic euvolaemic hyponatraemia in which the regulated osmolality set point is below normal.
Diagnostic / clinical pearl
In chronic euvolaemic hyponatraemia, consider a reset osmostat and use diagnostic testing to assess whether plasma osmolality is regulated around a lower set point.