Adrenocorticotropin-independent Macronodular Adrenal Hyperplasia: An Uncommon Cause of Primary Adrenal Hypercortisolism

To describe the imaging findings in the adrenal glands of 12 patients with adrenocorticotropin (ACTH)-independent macronodular adrenocortical hyperplasia (AIMAH).Computed tomographic (CT) and magnetic resonance (MR) imaging findings in the adrenal glands were reviewed retrospectively in 12 patients (three men, nine women) with ACTH-independent Cushing syndrome and with bilateral nonpigmented multinodular adrenal hyperplasia. The results of pituitary MR imaging, adrenal scintigraphy, and petrosal sampling were available in nine, five, and six patients, respectively. Eleven patients underwent bilateral and one patient underwent unilateral adrenalectomy.Eleven patients had enlarged multinodular adrenal glands: Nodules were 0.1-5.5 cm. The combined weight of both adrenal specimens for the 11 bilateral adrenalectomy specimens was 28-297 g, with a mean weight of 122 g. Glands were hypointense compared with the liver on T1-weighted images and were hyperintense on T2-weighted images. Pituitary MR imaging findings were negative in nine of nine patients. Iodomethylnorcholesterol scintigraphy showed bilateral uptake in four of five patients. Petrosal sinus sampling revealed no petrosal-to-peripheral ACTH gradients before corticotropin-releasing hormone (CRH) stimulation in six of six patients, but three patients had gradients after CRH stimulation. After undergoing bilateral or unilateral adrenalectomy, all patients were cured.AIMAH is a rare cause of ACTH-independent Cushing syndrome, with characteristic CT findings of massively enlarged multinodular adrenal glands. Bilateral adrenalectomy is indicated on the basis of clinical and CT findings.