A Difficult Case of Ectopic ACTH Syndrome: Is Treatment Possible Even Without Accurate Localization?

Occult ectopic adrenocorticotropic hormone (ACTH) syndrome (EAS) is a relatively rare form of ACTH-dependent Cushing's Syndrome (CS). We describe a middle-aged female with symptomatic CS, where despite thorough investigations including hormone suppression testing, multiple imaging modalities, and inferior petrosal sinus sampling (IPSS), an ectopic source could not be demonstrated. Our case demonstrates that ketoconazole can be an effective therapeutic to suppress cortisol production even when the source of ectopic ACTH production is unknown. However, long-term evaluation is required.