[Cushing's syndrome--unusual cases].

The separation of Cushing's disease from non-pituitary ACTH-secreting tumors is rarely straightforward. Both a 16-year-old girl and a 56-year-old man exhibited typical clinical features of Cushing's syndrome. In both patients urinary 17OHCS was suppressed by 8mg dexamethasone and plasma cortisol and ACTH responded to intravenous administration of CRH. X-rays of the skull, a computed tomographic scan and a magnetic resonance imaging (MRI) of the sella turcica area showed no significant abnormality. An enhanced MRI of the pituitary gland in the first patient demonstrated a small low-density area which represented microadenoma. In the second patient, an enhanced MRI and inferior sinus sampling failed to demonstrate a pituitary tumor. The patient died of acute myocardial infarction, and an autopsy revealed a bronchial carcinoid in the right upper pulmonary lobe. It is necessary to differentiate an ectopic ACTH-secretion in patients with Cushing's syndrome who show typical biochemical features of Cushing's disease but fail to demonstrate the presence of a pituitary tumor by routine radiological evaluation.