Authors’ response to letter by Adam Morton regarding: “Managing severe peripartum hyponatraemia: A case report”

We thank Dr Morton for his interest in our case report. He queries whether acute glucocorticoid deficiency could have been responsible for our patient’s symptoms. We agree with him that it is important to exclude adrenal insufficiency early in the investigation of patients with hyponatraemia to avoid the risks of missed diagnosis. However, physicians should take care in the interpretation of a normal cortisol result as this may not exclude the disease, particularly in the third trimester. A number of factors in our case lead us to exclude glucocorticoid deficiency. Firstly, she remained normotensive following fluid resuscitation for her haemorrhage-induced hypovolaemia. Secondly, whilst not shown in the case report, her potassium and blood glucose concentrations were within normal limits. Our patient’s sodium also initially responded to a saline infusion prior to her first discharge from the Intensive Care Unit. Had adrenal insufficiency been the cause this would not have been expected. Finally, her 09:00 serum cortisol concentration measured the morning after her stroke (when her hyponatraemia was first noted) was 403 nmol/l (range at 09:00, 171–536 nmol/ l). With these four factors, we felt glucocorticoid deficiency was unlikely. Dr Morton also highlights a case report of a presentation of Sheehan’s syndrome with acute secondary adrenal insufficiency characterised by hyponatraemia and hypoglycaemia. Whilst we concede that early presentation of secondary adrenal deficiency is possible, clearly this is unusual with a later presentation more typical.