Adrenal cortical adenoma causing Cushing's syndrome: correct localization by functional scintigraphy despite...

A 60-year-old woman with Cushing's syndrome in whom high-dose dexamethasone failed to suppress glucocorticoids was studied by ultrasound and CT. Neither of these morphological studies was interpreted as revealing any adrenal abnormality. Functional imaging with NP-59 (131-I-beta-iodomethylnorcholesterol) revealed unequivocal, intense, unilateral uptake in the left adrenal gland and subsequent surgery removed a 2.5 cm adrenocortical adenoma from this site. Following surgery the patient was temporarily adrenocortically insufficient but later returned to normal. It is unusual for adrenocortical adenomas causing Cushing's syndrome not to be correctly located by CT. NP-59 scintigraphy in addition to being highly accurate in the location of adrenocortical adenomas also has the advantage of correctly depicting bilateral cortical nodular hyperplasia in which CT will frequently reveal only the largest nodule, which may be incorrectly designated a unilateral adenoma. Furthermore, scintigraphy provides evidence of suppression of the contralateral, normal adrenal cortical tissue in Cushing's syndrome caused by an adrenal adenoma and predicts the vulnerability of such patients to postoperative adrenocortical insufficiency.