title: Occult eutopic Cushing's syndrome--failure of simultaneous bilateral petrosal sinus sampling to diagnose pituitary-dependent Cushing's syndrome.
abstract: Simultaneous bilateral inferior petrosal sinus (IPS) sampling has been repeatedly proposed to be a highly specific approach for the diagnosis of Cushing's disease and 100% sensitivity in detecting autonomous pituitary ACTH secretion by an adenoma has been reported in a large series. We now report on a patient suffering from ACTH-dependent Cushing's syndrome in whom repeated bilateral IPS sampling failed to detect a central/peripheral gradient diagnostic for autonomous pituitary ACTH secretion during initial evaluation. Applying lysine vasopressin as the corticotroph secretatogue, the maximum central/peripheral gradient was 1.0 before and 1.1 following stimulation. Moreover, results of high dose dexamethasone and corticotrophin releasing hormone administration suggested ectopic ACTH secretion. Since thorough diagnostic procedures failed to localise a suspected carcinoid tumour, occult ectopic Cushing's syndrome was diagnosed. Eight years later, a pituitary macroadenoma was detected by magnetic resonance imaging (MRI), IPS catheterisation then revealed a maximal central/ peripheral gradient of 9.3 before and 20.4 after the intravenous administration of lysine vasopressin. Resected tumour tissue was classified as a typical densely granulated ACTH cell adenoma. We conclude that repeated MRI scans should be included in the follow-up of patients with a diagnosis of occult ectopic Cushing's syndrome to avoid the risk of overlooking 'occult eutopic Cushing's syndrome'.
authors.affiliation: Department of Medicine II, University of Cologne, Germany.
authors.forename: C
authors.initials: C
authors.lastname: Heppner
authors.forename: K
authors.initials: K
authors.lastname: Becker
authors.forename: W
authors.initials: W
authors.lastname: Saeger
authors.forename: R W
authors.initials: RW
authors.lastname: Günther
authors.forename: B
authors.initials: B
authors.lastname: Allolio
authors.forename: W
authors.initials: W
authors.lastname: Krone
authors.forename: W
authors.initials: W
authors.lastname: Winkelmann
mesh_terms: D000236:Adenoma / Q000175:diagnosis / Q000378:metabolism*; D000324:Adrenocorticotropic Hormone / Q000378:metabolism*; D000328:Adult; D003346:Corticotropin-Releasing Hormone; D003480:Cushing Syndrome / Q000175:diagnosis*; D003907:Dexamethasone; D005188:False Negative Reactions; D005260:Female; D006801:Humans; D008236:Lypressin; D008279:Magnetic Resonance Imaging; D017591:Petrosal Sinus Sampling; D010902:Pituitary Gland / Q000378:metabolism; D010911:Pituitary Neoplasms / Q000175:diagnosis / Q000378:metabolism*; D014057:Tomography, X-Ray Computed
chemical_list: D008236:Lypressin; D003907:Dexamethasone; D000324:Adrenocorticotropic Hormone; D003346:Corticotropin-Releasing Hormone