Diagnosis of Cushing's Disease.

Cushing's disease (CD), the most common cause of Cushing's syndrome (CS), is ideally treated by resection of the underlying ACTH-producing pituitary adenoma. However, it may be difficult to establish that CD is the underlying etiology of CS. In this article, we outline a suggested diagnostic approach and discuss common pitfalls, from initial screening for hypercortisolism through the evaluation of ACTH-dependence and confirmation of the presence of a pituitary tumor using imaging and biochemical testing. Most diagnostic steps should preferably take place at a center specialized in pituitary disorders that uses optimized MRI techniques, has access to bilateral inferior petrosal sinus sampling, and an experienced pituitary surgeon.