Endocrine Abstracts

A 24 yr old man complaining of visual disturbances for 7 weeks presented with acute severe headache and bitemporal visual field defects. A high density lesion in the pituitary fossa suggestive of pituitary apoplexy was initially observed on a CT scan but an MRI of the pituitary revealed an irregular structure in the suprasellar cistern and the differential diagnoses of a pituitary adenoma or an aneurysm were proposed. Routine haematological and biochemical investigations were normal as were prolactin, TSH, FSH, LH, GH, IGF1 concentrations. Random cortisol concentration was low at 15 nmmol/l. Transsphenoidal exploration of the pituitary fossa revealed a normal pituitary gland and fossa and the patient underwent a further craniotomy that revealed that the left optic nerve and chiasm were compressed by either a thrombosed infraclenoid ophthalmic artery aneurysm or a suprasellar tumour with haemorrhage. The lesion was excised and histological appearance was that of a haematoma with fibrous capsule consistent with part of an aneurysm. There was no evidence of neoplasia. Post operatively investigations revealed normal LH, FSH response to GnRH stimulation, normal TSH response to TRH stimulation, normal GH response to hypoglycaemia on an Insulin tolerance test, but a reduced cortisol response to hypoglycaemia (peak value 280 nmol/l at 90 minutes), long synacthen test and glucagon stimulation test(peak value 392 nmol/l at 180 minutes). The possible pathophysiological mecahanisms by which aneurysms can affect pituitary hormone secretion include direct hypothalmo-pitutary compression, pressure from haemorrhage and damage by toxic effects of extravasated subarachnoid blood, intracranial hypertension or vasospasm after subarachnoid haemorrhage. We report a case of spontaneous thrombosis of an ophthalmic artery aneurysm as a novel cause of isolated cortisol deficiency.