Electrolyte Derangements when Ectopic Cushing’s Is Included in Dual Paraneoplastic Syndrome

Although ectopic adrenocorticotropic hormone (ACTH) syndrome is typically characterized by hypokalemia, which may be refractory to treatment, as in the recently reported case,1 the occasional patient presents with concurrent hyponatremia, as depicted in several case studies.2-5 This biochemical association is attributable to the rarely reported paraneoplastic syndrome of coexistence of ectopic ACTH secretion and syndrome of inappropriate antidiuretic hormone secretion.2-4 The underlying cause was small-cell lung cancer in all 11 fully investigated cases.