Endocrine Abstracts

A 52 year old man presented 5 years ago with a history of persistent rhinorrhea, blocked nose and epistaxis. MR scanning revealed blockage of the ethmoid sinus with polypoidal material extending into the nasopharynx, anterior cranial fossa and right orbit. He had craniofacial resection of the lesion and histology confirmed an olfactory neuroblastoma.

He represented in 2005 with a two-week history of generalized weakness, lack of energy, and bilateral ankle oedema. Initial investigations revealed hypokalemic metabolic alkalosis (K+2.2 mmol/l and venous bicarbonate 44 mmol/l) suggesting hypercortisolism. This was supported by morning serum cortisol of 1630 nmol/l (range 171–536 between 0700–1000), serum adrenocorticotropic hormone (ACTH) 388 ng/l (0–47), and 24-hour urinary free cortisol 13667 nmol/d (40–305). Other basal anterior pituitary hormones were normal. MRI scan of the brain confirmed a recurrence of the olfactory neuroblastoma at the left frontal sinus with dural deposits. He is being treated with metyrapone 500 mg tds.

This presentation seems most likely to be due to ectopic secretion of ACTH from recurrent olfactory neuroblastoma as suggested by a short history, significant hypokalemia, marked elevation of the cortisol and ACTH and lack of other classical clinical features of long standing hypercortisolism. High dose dexamethasone suppression test was not performed because the clinical, biochemical and radiological evidence supported ectopic ACTH secretion. Olfactory neuroblastoma seems the most likely source. Normal chest x-ray, CT trunk and pituitary gland on MR scanning make ACTH secretion from another source unlikely.