Correction of metabolic alkalosis by potassium chloride in ectopic adrenocorticotropic hormone syndrome.

A 57-year-old white man presented with metabolic alkalosis, hypokalemia (pH 7.58, HCO3 >50 mEq/L, serum K 1.8 mEq/L) and hypertension. The initial evaluation was significant for markedly elevated serum cortisol and adrenocorticotropic hormone (ACTH) level; neither hormone showed circadian rhythm or suppression with high-dose dexamethasone. Perihilar and supraclavicular masses were found to consist of undifferentiated small cell carcinoma. Ectopic ACTH syndrome was diagnosed. In spite of progressively rising hormone levels (ACTH, 723 pg/dL; and cortisol, 212 microgram/dL), his severe metabolic alkalosis was largely corrected by aggressive treatment with potassium chloride alone. Possible mechanisms of these clinical findings are discussed.