Inconsistent stimulation of plasma ACTH through corticotropin-releasing factor in a patient with central Cushing's disease due to pituitary adenoma

Three uncommon findings were observed in a case of Cushing's
disease due to macroadenoma: no suppression of plasma ACTH during
an 8-mg dexamethasone test, a negative corticotropin-releasing
factor test, and a normal X-ray of the sella turcica. Despite these
findings, the diagnosis of pituitary was confirmed Cushing's
syndrome by computerized tomography and a transphenoidal operation.