Diagnostic and therapeutic challenges in ectopic Cushing’s syndrome without detectable tumour focus – a case report

Ectopic adrenocorticotropin (ACTH) secretion is a rare cause of Cushing's syndrome, often posing a diagnostic challenge, particularly when the source of excessive ACTH secretion cannot be localized.The case is presented of a 70-year-old woman with Cushing's syndrome caused by ectopic ACTH secretion from an elusive location.Despite extensive imaging (CT, MRI, PET/CT with 68Ga-DOTATATE), no tumour site could be identified.Metyrapone led to normalization of cortisol and ACTH levels and a two-year remission.After a recurrence of hypercortisolaemia, osilodrostat therapy was initiated, achieving renewed hormonal and clinical stabilization.This case highlights the importance of pharmacotherapy with steroidogenesis inhibitors as an effective alternative to surgery in patients with an unlocalized source of ectopic ACTH secretion, and the need for long-term endocrine follow-up.