Testing to establish the cause of Cushing's syndrome*

ACTH: corticotropin; CRH: corticotropin-releasing hormone; CT: computed tomography; MR: magnetic resonance; MRI: magnetic resonance imaging; dex: dexamethasone; IPSS: inferior petrosal sinus sampling.
* Testing can only be interpreted in the context of sustained hypercortisolism and may be inaccurate with cyclic hypercortisolism.