Background: Phaeochromocytoma represents a rare cause of hypercortisolism, accounting for <5% of ectopic Cushings syndrome while <1% of phaeochromocytomas are accompanied by Cushings syndrome.
Case presentation: We present a case of a 51-year-old lady admitted to the surgical ward for bowel surgery for severe long-standing constipation. She was referred to the endocrine team for recent-onset severe hypokalaemia and the presence of left-sided lipid-rich adrenal adenoma on abdominal CT scan. She had 10-year history of episodic headaches, flushing, sweating, palpitations, and hypertension. Type-2 diabetes diagnosed 6 years ago was sub-optimally controlled on maximal oral therapy. On examination, she did not have typical cushingoid appearance although she did have facial hirsutism, marked proximal muscle weakness, and extensive oral candidiasis that affected her oral intake and nutrition.
Investigations: Initial tests revealed severe hypokalaemia (2.4 mmol/l) and hypercortisolism (2089 nmol/l), which was unsuppressed by 1 and 8 mg dexamethasone. ACTH level was 855 ng/l suggesting ACTH driven Cushings syndrome. Androstenedinone level was disproportionately raised (126 nmol/l). Urinary catecholamines and fractionated metanephrines were raised 30-fold. 131I MIBG scintigraphy was negative but 68Ga-DOTA-PETCT scan confirmed that the left adrenal mass was the source of excessive catecholamine production with no evidence of metastasis.
Diagnosis: In view of severe and non-suppressible hypercortisolaemia, high ACTH, elevated catecholamines, and an adrenal mass with a positive PET scan a diagnosis of phaeochromocytoma with ectopic ACTH production was made.
Management: Over the next few weeks she was managed with oral potassium, spironolactone, insulin and block-replacement therapy with metyrapone and dexamethasone. She underwent adrenalectomy following adequate preparation with a combination of phenoxybenzamine and propranolol. Histology confirmed the diagnosis of phaeochromocytoma, which stained positive for ACTH on immunochemistry. Post adrenalectomy she remained normotensive without medication, her constipation resolved, and glycaemic control was excellent on single oral agent. 24-h urine for total catecholamines, metanephrines, returned within normal limits. Hypercortisolism resolved although HPA axis remained suppressed 6 weeks after surgery requiring continuation of replacement steroids.