Endocrine Abstracts

A 60-year-old woman was referred with a 14 mm right adrenal mass on a contrast CT abdomen whilst being investigated for left iliac fossa pain and increased bowel frequency. She reported a 2-year history of anxiety attacks, poor sleep, excessive sweating and weight loss. She had hypertension, asthma and recurrent vasovagal syncope and had previously undergone an open cholecystectomy. Her medications included Lansoprazole, Salbutamol, Losartan, Citalopram and Diltiazem. Systemic and abdominal examination was unremarkable. Her blood pressure was normal.

Investigations showed normal FBC, U&Es, LFTs, TSH and glucose. Further biochemical tests showed normal renin and aldosterone levels, DHEAS, and 1 mg overnight dexamethasone suppression test (cortisol 12 nmol/l). She had four 24 h urinary measurements for catecholamines and metanephrines all of which were normal. Plasma metanephrines were mildly elevated (735 pmol/l; normal range: 80–510) on Citalopram and Diltiazem but repeat measurements following discontinuation of medications were normal (133 pmol/l).

A further non-contrast CT and MRI of the abdomen showed a low attenuation lesion and high signal on T2 weighted images respectively in the right adrenal nodule. MIBG showed significantly elevated tracer activity in the right adrenal nodule.

The patient was counselled about the uncertainty of the diagnosis, risks of surgery and the likelihood that her symptoms may not be cured. After preoperative preparation with maximally tolerated doses of phenoxybenzamine, she underwent retroperitoneoscopic right adrenalectomy. During the procedure, there was clear evidence of blood pressure lability (fluctuations) during tumour manipulation, consistent with a phaeochromocytoma. Her recovery was uneventful. Histology confirmed phaeochromocytoma. Her symptoms resolved and there was a significant drop in plasma metanephrines post-operatively (<40 pmol/l).

This is a rare case of undetectable catecholamine and metabolites in a symptomatic patient with radiological and histological evidence of a small phaeochromocytoma and highlights the importance of symptoms and imaging in the diagnosis of phaeochromocytoma.