Endocrine Abstracts

Introduction: SIADH is a disorder of sodium and water balance characterized by hypotonic hyponatremia and impaired urinary dilution in the absence of renal disease or any identifiable non-osmotic stimulus known to relase ADH. SIADH is usually observed in hospitalized patients and its prevalence may be as high as 35%.

Case Report: A 70 year old women was admitted to the Medicine and Rehabilitation Clinical Institute of Aosta on October 2011. She had a change of mental status. Physical examination was normal. There was a vesicular erythematous rash at the chest level, which was consistent with a diagnosis of HZI. The patient was disoriented and confused. Laboratory results showed blood count in the normal range, serum concentration of sodium was 119 mEq/l, potassium 4 mEq/l, creatinine 0.8 mg/ml. Urine sodium was 45 mEq/l and potassium 50 mEq/l. Urine was highly concentrated with an osmolality of 620 mOsm/kg H₂O, while plasma osmolality was 243 mOsm/kg H₂O. Thyroid and adrenal function was normal. Plasma antidiuretic hormone (ADH) was 3.8 pg/ml (normal range 0.3–3.5 pg/ml). Given these results, a diagnosis of SIADH was made. Under water restriction, infusion of 3% saline, treatment with loop diuretics and with complete acyclovir therapy, mental function returned to normal within 2 day. Seven day later, serum sodium concentration was increased to 136 mEq/l with plasma osmolality of 275 mOsm/kg.

Conclusion: We postulate that although the association between HZI and SIADH has been rarely reported in the literature, this is likely to be an under representation of its true incidence.

Declaration of interest: The authors declare that there is no conflict of interest that could be perceived as prejudicing the impartiality of the research project.

Funding: This research did not receive any specific grant from any funding agency in the public, commercial or not-for-profit sector.