Post-traumatic hyponatraemia due to acute hypopituitarism.
Sir,

Hyponatraemia following traumatic brain injury (TBI) is a common complication, occurring in 13% of cases.1 The commonest cause of hyponatraemia is the syndrome of inappropriate antidiuretic hormone secretion (SIADH), which is responsible for over 90% of cases,1 whereas cerebral salt wasting, medications and injudicious use of intravenous fluids may also cause hyponatraemia following TBI. As glucocorticoid deficiency can present with hyponatraemia similar to that found in SIADH, it is essential to exclude adrenal insufficiency before making a diagnosis of SIADH.2 This may be of particular importance in the case of TBI, as recent data have indicated a high frequency of undiagnosed hypopituitarism among long-term survivors.3 In addition, 16% of acute head injury patients show biochemical …