Endocrine Abstracts

Background: Cushing’s syndrome derived from paraneoplastic ectopic ACTH production can present in dramatic fashion. We describe such a case that presented with severe hypokalaemia, involving significant diagnostic and management challenges.

The case: A 66-year-old female was referred acutely to hospital by her GP after feeling weak and lethargic. She had profound hypokalaemia of 1.5 mmol/l (3.5–5.3) with normal renal function and had been normokalaemic 6 weeks earlier. Past history included previous localised breast cancer and a metastatic bladder carcinoma – with evidence of findings in the lungs and liver – the latter had undergone partial resection. Her medication was furosemide 20 mg (which had been started a week ago), amlodipine 5 mg, simvastatin 40 mg, and anastrazole 1 mg. On examination: pulse 90 bpm, BP 140/80, and she had massive generalised oedema. She was admitted to critical care. Investigations showed ABG pH 7.61 (7.35–7.45) and HCO₃ 56 (22–30). Random glucose was 6.8, prolactin 230, TSH 0.72 and FT₄ 12.0. Emergency management was initially intravenous potassium replacement. An endocrine consultation noted a clearly Cushingoid appearance. Further investigations revealed 0900 cortisol of 5957 nmol/l and after an overnight 1 mg dexamethasone suppression test 5595 nmol/l. An aldosterone:renin ratio was normal at 320. The primary bladder tumour histology was reported as showing small cells exhibiting neuroendocrine differentiation with strongly CD56++ and Synaptophysin++. In order to suppress her cortisol, she was commenced on metyrapone titrated to 100 mg tds with clinical and biochemical benefit. She was later transferred to a hospice.

Conclusion: This patient presented with a hypokalaemic Cushing’s crisis and profound metabolic alkalosis exacerbated by recent exposure to furosemide. Ectopic ACTH causes <10% of cases of Cushing’s and only very few of those have been reportedly due to small cell carcinoma arising from the bladder. This case thus provided profound insights into the care of such patients.