Hypokalaemia: common but not always benign. Severe, persistent hypokalaemia secondary to ectopic ACTH from a carcinoid tumour.

Hypokalaemia is a common and often benign observation. There is usually an obvious underlying cause for the anomaly. However, hypokalaemia can very rarely be the sole presentation of a more sinister disease. A high index of suspicion and a systematic approach are therefore required to avoid delays in the management, especially in the context of presentation to a medical team. We present a case of a patient with severe and persistent hypokalaemia due to ectopic adrenocorticotropic hormone (ACTH) secretion secondary to a carcinoid tumour. The case report is followed by a brief discussion on the approach to the management of hypokalaemia and additional tests to confirm ectopic ACTH.