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A 47-year-old man presented with severe clinical hypoglycaemia. He had long-standing insulin-dependent diabetes with previously good glycaemic control. Intense headaches and vomiting initiated hospitalization. A brain computed tomography (CT) scan was normal, and a lumbar puncture showed elevated cerebrospinal fluid (CSF) protein [0.67 g/L; normal range (NR) 0.15-0.45 g/L], suggesting resolving viral meningitis. Routine thyroid function tests were abnormal (free thyroxine 10.6 pmol/L, NR 9-22.5 pmol/L; thyroid-stimulating hormone 0.16 mU/L, NR 0.35-5 mU/L). In the absence of evident thyroid therapy, the laboratory policy required an urgent cortisol assay to be added; this was very abnormal (42 nmol/L), suggesting hypopituitarism. Later analysis showed that concentrations of gonadotrophins and adrenocorticotrophin were low. An urgent pituitary magnetic resonance imaging scan revealed an unsuspected pituitary tumour with recent haemorrhage (pituitary apoplexy). The patient was given intravenous hydrocortisone and then stabilized on oral hydrocortisone, thyroxine and mesterolone. He made a full recovery and the hypoglycaemia resolved. The normal brain CT scan was falsely reassuring and the CSF protein was not due to viral meningitis but to haemorrhage into the pituitary tumour. If laboratory policy had not required the urgent cortisol assay be added, the diagnosis of hypopituitarism would have been delayed or even missed altogether. This could have led to the death of the patient.