Copeptin; utility in paediatric patients with hyponatraemia.

Introduction Copeptin concentrations are a useful component of the diagnostic work-up of paediatric patients with polyuria and polydipsia but the value of measuring copeptin in patients with hyponatraemia is less clear. Case Reports We report 5 children with hyponatraemia in the context of different underlying pathologies. Copeptin concentrations were elevated in 4 cases (13.7, 14.4, 26.1, 233pmol/L; reference range 2.4 - 8.6pmol/L) suggesting that non-osmoregulated vasopressin release (syndrome of inappropriate antidiuretic diuretic hormone or SIADH) was the underlying mechanism for the low sodium levels. In one of the patients there was an underlying diagnosis of Schaaf-Yang syndrome (MAGEL 2 gene mutation) with a clinical picture suggestive of dysregulated vasopressin production with inappropriately high and then low copeptin release. In one hyponatraemic patient, low copeptin concentrations indicated that non-osmoregulated AVP release was not the cause of hyponatraemia and oliguria. Discussion Copeptin measurement did not influence management acutely but helped to clarify the mechanism leading to hyponatraemia when the result was available. Relatively high and low copeptin concentrations in association with hypo and hypernatraemia indicates dysregulated vasopressin production in Schaaf-Yang syndrome. Profound copeptin elevation may be a clue to underlying sepsis.