Hypokalemia associated with a solitary pulmonary nodule: A case report

BACKGROUND: Differential diagnosis of hypokalemia and adrenocorticotropic hormone (ACTH)-dependent Cushing's syndrome often presents challenging in endocrinology and requires careful clinical, biochemical, radiological, and pathological investigations. Hypokalemia is a common abnormality and systematic approach is required to avoid delays in diagnosis of important underlying causes. CASE SUMMARY: A 49-year-old woman presented with moderate hypokalemia. Further evaluation showed hypercortisolism due to ectopic ACTH secretion. Chest computed tomography (CT) revealed a peripheral solitary pulmonary nodule. Excision biopsy of the nodule showed carcinoid tumor. After excision biopsy, all of the patient's symptoms improved and electrolytes and ACTH levels also became normal. CONCLUSION: Carciniod tumors should be considered as a differential diagnosis in patients presenting with hypokalemia and ectopic ACTH syndrome. Carcinoid tumor often present as solitary pulmonary nodule and excision biopsy can be curative.