Efficacy of iodine-131 6 beta-methyl-iodo-19-norcholesterol scintigraphy and computed tomography in patients with primary aldosteronism

In order to define the role of scintigraphy in determining the aetiology of primary aldosteronism, 41 patients were examined by computed tomography (C T) scan and adrenal scintigraphy using iodine-131 6 beta-methyl-iodo-19-nor cholesterol with the dexamethasone suppression test. Hormonal and scintigra phic examinations were conducted while avoiding interference by medical tre atment. The aetiological diagnosis was established by taking account of the clinical context, the endocrine profile, and CT scan and scintigraphic dat a, as well as possible hormone assays after catheterization of the adrenal veins(12 cases) and postoperative pathology data (14 cases). The aetiologic al diagnoses established were Conn's adenoma (insensitive to angiotensin II ) in 12 cases, idiopathic hyperplasia in 11 and macronodular hyperplasia (w ith functional autonomy of the nodules) in 18. Unilateral and bilateral les ions were correctly distinguished by scintigraphy in 92% of cases as compar ed with only 58% using CT scan alone; this was because the CT scan appearan ce was normal in 3/12 cases of adenoma and because a single nodule was visi ble in 2/11 cases of idiopathic hyperplasia and in 12/18 cases of macronodu lar hyperplasia. It is concluded that scintigraphy using noriodocholesterol with the dexamethasone suppression test should be performed systematically in conjunction with hormonal tests and adrenal CT scan in all cases of pri mary aldosteronism, as part of a strategy aimed not only at detecting adeno ma but also at determining whether the hyperfunctional lesions are bilatera l.