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Abstract
Chronic hypernatraemia is a rare clinical entity. In the younger population, hypernatraemia is often a consequence of failure to generate thirst in response to osmotic stimuli.
We report the case of a male patient admitted with severe hypernatraemia (plasma sodium 175 mmol/L) on return from holidays. His urine was maximally concentrated at 894 mOsm/kg—suggestive of normal vasopressin reserve. MRI of the brain showed a large extra-axial cyst, with preservation of the posterior pituitary bright spot. Formal osmoregulatory studies demonstrated normal osmoregulated vasopressin secretion and normal thirst, but no appropriate drinking behaviour.
This patient illustrates a unique pathophysiological disconnect between thirst appreciation and the central drive to drink, in the context of normal osmoregulatory function. It is likely that this disconnect is related to the patient’s large intracranial cyst.
The management challenge is to maintain appropriate fluid intake in order to prevent recurrent severe hypernatraemia.
- Pituitary disorders
- Fluid electrolyte and acid-base disturbances
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Footnotes
Contributors RMT, MS, CT were responsible for drafting of the text, sourcing and editing of clinical images, investigation results, drawing original diagrams and algorithms, and critical revision for important intellectual content. CT gave final approval of the manuscript.
Funding The authors have not declared a specific grant for this research from any funding agency in the public, commercial or not-for-profit sectors.
Case reports provide a valuable learning resource for the scientific community and can indicate areas of interest for future research. They should not be used in isolation to guide treatment choices or public health policy.
Competing interests None declared.
Provenance and peer review Not commissioned; externally peer reviewed.