Role of I-NP-59 Adrenal Imaging in Patients of ACTH-Independent Cushing’s Syndrome

Received 11/10/2000; revised 2/15/2001; accepted 2/26/2001. For correspondence or reprints contact: Chiang-Hsuan Lee, M.D., Department of Nuclear Medicine, Chang Gung Memorial Hospital, 123, Ta Pei Road, Niao Sung Hsiang, Kaohsiung Hsien, Taiwan, R.O.C. Tel: (886)7-7317123 ext. 2627, Fax: (886)7-7317123 ext. 2631, E-mail: [email protected] Background: Iodine-131-6-β-iodomethyl-19-norcholesterol (I-NP-59) imaging is a noninvasive adrenal imaging study that enables localization and characterization of endocrine dysfunction in the adrenal cortex. Herein, we report on our 12-year experience with I-NP-59 imaging in the localization of ACTH-independent Cushing’s syndrome. Methods: We reviewed the records of 25 ACTH-independent Cushing’s syndrome patients who had undergone adrenal scintigraphy in our hospital between January 1988 and August 2000. All patients underwent I-NP-59 imaging and CT scanning before adrenalectomy and had pathologic examinations. Results: I-NP-59 imaging correctly identified adrenocortical adenomas in 90% (18/20) of the cases. In adrenocortical carcinoma, the classic scintigraphic pattern of bilateral nonvisualization was observed in 1 of 3 patients, with visualization on the side of the tumor in 2 patients. CT scanning correctly depicted the adrenal lesions in all cases of adenoma and carcinoma except for one case of carcinoma in which bilateral adrenal hyperplasia was demonstrated. In cortical nodular hyperplasia, both I-NP-59 imaging and CT scanning showed negative results in bilateral micronodular dysplasia and correctly identified the bilateral nature of bilateral ACTH-independent macronodular hyperplasia. Conclusions: The interpretation of adrenal scintigraphy is not only directly dependent upon the results of biochemical studies, but it also is affected by intradiagnostic medications and hyperlipidemia. Unilateral visualization of an adrenal tumor on I-NP-59 imaging cannot be uniformly interpreted to represent benign disease.