CLINICAL STUDY c v

The diagnosis of Cushing’s syndrome (CS) is often a challenge because it is still difficult to differentiate between an adrenocorticotrophic hormone (ACTH)-secreting pituitary adenoma (Cushing’s disease; CD) and the rare form of ectopic ACTH secretion by tumors. Pituitary magnetic resonance imaging (MRI) should be performed in all patients with suspected ACTH-dependent CS, but this may reveal pituitary adenoma in no more than 36–78 % of cases in adult series (1–5). It is also important to bear in mind that the pituitary gland may harbor incidental tumors in the general population too, since autopsy studies have shown that 10–20 % of normal individuals have pituitary microadenomas (6). In the diagnostic approach to CS, endocrinologists have to deal with two different problems, i.e., the possibility o