Acute Severe Cushing Syndrome: Not Always Ectopic Acth Syndrome

ABSTRACT Objective: Cushing syndrome (CS) is a rare disease that results from prolonged supraphysiologic tissue action of glucocorticoids. Cushing disease is the most frequent cause of endogenous CS and is associated with increased morbidity and mortality. Disease onset and severity reflects the magnitude of cortisol excess, and ectopic adrenocorticotropic hormone (ACTH) syndrome is the most frequent cause of acute, severe CS. Cushing disease tends to have a slower onset with gradual appearance of the typical phenotype and associated metabolic consequences. Methods: Case report and review of the literature. Results: A 62-year-old man was admitted for altered mental status, severe hyperglycemia, and refractory hypokalemia. Despite clinical and biochemical presentation being suggestive of ectopic ACTH secretion, an ACTH-secreting pituitary adenoma was the underlying cause. Endoscopic transsphenoidal tumor excision led to disease remission. Conclusion: The case is noteworthy for the atypical clinical presentation, severity of the hypokalemia, and excellent treatment outcome. The biochemical testing has limitations, and these should be kept in mind in the investigation of hypercortisolism. Abbreviations: ACTH adrenocorticotropic hormone; CD Cushing disease; CS Cushing syndrome; CT computed tomography; EAS ectopic ACTH secretion; MRI magnetic resonance imaging