Failure of Dexamethasone Suppression Test To Indicate Bilateral Adrenocortical Hyperplasia in Cushing's Syndrome

Abstract

A patient with Cushing's syndrome secondary to bilateral nodular adrenocortical hyperplasia is described, in whom large doses of dexamethasone did not suppress urinary 17-OHCS excretion. Hyperresponsiveness to ACTH, however, was found. Following total bilateral adrenalectomy, the Cushing's syndrome slowly subsided and there has been no evidence of extra-adrenal malignancy. The adrenals demonstrated cortical hyperplasia with multiple small cortical nodules bilaterally and one large (23 mm) cortical nodule in the left gland. It is concluded that in certain unusual patients with Cushing's syndrome and bilateral adrenocortical hyperplasia (and presumably without extra-adrenal malignancy) there may be a lack of suppression to dexamethasone in the presence of ACTH hyperresponsiveness, which probably reflects a more severe and complicated disturbance in the regulation of pituitary corticotrophic activity.