Subclinical Cushing syndrome and adrenal incidentaloma

Agnieszka Falinska, Thein Htay, Daniel Morganstein, Alison Wren

Department of Endocrinology, Chelsea and Westminster Hospital Foundation Trust

Case report:

A 50-year old patient was referred with a 2.5cm adrenal mass incidentally identified on CT performed for complications of hiatus hernia operation. She was treated for hypertension for three years previously and suffered from glaucoma. Both her mother and grandmother also had hypertension. She was on Amlodipine 10mg only but Bendroflumethiazide and Candesartan were stopped pre-operatively. On initial assessment for adrenal hyper-function she was found to be hypertensive (144/96) and had a history of weight gain, occasional palpitations and easy bruising. There was no evidence of proximal myopathy, thin skin or striae. Her investigations showed:

-       normal UE (potassium 4.9) and aldosterone/renin ratio

-       normal 24-hour urinary catecholamines and free metanephrines;

-       24-hour urinary free Cortisol (UFC) mid normal range x3 (complete collections)

-       unchanged right adrenal adenoma 2.5 cm x 1.5 cm on repeated CT scans over 2 years

-       failure to suppress Cortisol (114) following overnight Dexamethasone suppression

-       twice failure to suppress cortisol on repeated LDST (48h cortisol 117 and 101 with ACTH undetectable consistent with autonomous cortisol production from adrenal source)

-       bilateral comparable cortisol production on adrenal vein sampling

Discussion: Whilst complete 24 hour urine cortisol was completely normal on two occasions there was failure of overnight and low dose dexamethasone suppression tests with undetectable ACTH, suggesting autonomous adrenal cortisol production. A non-dexamethasone suppressed morning cortisol was 334 with undetectable ACTH, suggesting suppression of ACTH-driven cortisol production in the basal state. She underwent adrenal sampling to investigate whether the source of excess cortisol was unilateral or bilateral (with a view of future laparoscopic adrenelectomy). However, adrenal vein sampling failed to lateralise cortisol production. This may suggest autonomous bilateral nodular adrenal hyperplasia hence unilateral adrenelectomy would not provide cure. Or has physiological stress of adrenal vein sampling promoted ACTH-dependent cortisol production, obscuring lateralisation. Currently the patient has gained 1-2kg weight, is normotensive on Amlodipine 10mg and Indapamide 2.5 mg, 24h UFCs remain normal and she is due for cortisol day curve.

This case raises questions about the future management options symptomatic and monitoring or uni/bilateral adrenelectomy? Furthermore - what further investigations would be most beneficial to lateralise and/or describe the lesion? Will adrenal sampling following dexamethasone suppression test add to characterising the mass? Will 11C-metomidate positron emission tomography after dexamethasone suppression be helpful? We welcome a discussion regarding these issues.