An unusual case of ectopic adrenocorticotrophic hormone syndrome and syndrome of inappropriate antidiuretic hormone secretion

Ectopic adrenocorticotrophic hormone (ACTH) syndrome (EAS) is a rare but severe condition characterized by intense hypercortisolism, which can occur independently of the underlying tumor. Surgical resection of the primary lesion is curative in approximately 40% of patients with EAS, and up to 80% of these cases result in complete remission. Therefore, localizing the source of EAS is crucial. We report an unusual case of a patient presenting with both EAS and syndrome of inappropriate antidiuretic hormone secretion, characterized by hypokalemia and hyponatremia, in the absence of classic manifestations of Cushing’s syndrome. Following the resection of an ACTH-negative staining tumor located in the right sellar nodule, the patient achieved complete remission. The study findings indicate that physicians should pay more attention to electrolyte disturbances, as they are crucial for diagnosing occult EAS.