Sub-clinical Cushing's syndrome in patients with adrenal gland incidentalomas. Pitfalls in diagnosis and management.

Widespread use of contemporary imaging techniques (ultrasound, computerized axial tomography, and magnetic resonance imaging scans) have led to the incidental discovery of asymptomatic adrenal neoplasms with increasing frequency. Patients with such adrenal "incidentalomas" typically have no clinical manifestations of adrenal cortical hyperfunction at the time of discovery. We have studied 122 patients with asymptomatic adrenal masses ranging in size from 2 to 7 cm in diameter from 1978 to 1988. Selected patients, after adrenal metastases, pheochromocytoma, myelolipomas, and cysts were ruled out, were further evaluated for adrenal cortical hyperfunction by measuring urinary 17-hydroxysteroids, 17-ketosteroids, and free cortisol, serum A.M., P.M. cortisol, and plasma ACTH levels. These values were also measured before and after dexamethasone suppression. NP-59 adrenal scintiscans were performed on all patients. Six patients were identified with sub-clinical Cushing's syndrome. Baseline cortisol levels were normal in each of these patients. Loss of diurnal rhythm appeared to be the most sensitive indicator of abnormal adrenal cortical function. When adrenalectomy is performed in such patients, especially when contralateral adrenal gland suppression is evidenced by NP-59 scanning or other biochemical assessment, perioperative steroids should be administered in a manner similar to that used for patients with symptomatic Cushing's syndrome. Unilateral adrenalectomy in a patient with an asymptomatic adrenal adenoma, insufficiently studied, may result in Addisonian crisis.