Among the causes of Cushing's syndrome are three rare types of nodular adrenocortical diseases that are usually bilateral:
- Corticotropin (ACTH)-dependent bilateral macronodular hyperplasia secondary to long-term adrenal stimulation in patients with Cushing's disease or ectopic ACTH syndrome
- ACTH-independent micronodular adrenal hyperplasia and its most frequent variant primary pigmented nodular adrenocortical disease (PPNAD), which may be sporadic or familial (as part of the Carney complex)
- ACTH-independent bilateral macronodular adrenal hyperplasia (AIMAH)
ACTH-independent bilateral macronodular adrenal hyperplasia will be reviewed here. Other causes of Cushing's syndrome, and primary pigmented nodular adrenocortical disease are discussed separately. (See "Causes and pathophysiology of Cushing's syndrome" and "Cushing's syndrome due to primary pigmented nodular adrenocortical disease".)
ACTH-independent macronodular adrenal hyperplasia (AIMAH) has been described by various terms, including massive macronodular adrenocortical disease (MMAD), autonomous macronodular adrenal hyperplasia (AMAH), ACTH-independent massive bilateral adrenal disease (AIMBAD), and "giant" or "huge" macronodular adrenal disease. AIMAH results in hypercortisolism through a number of mechanisms that are described below. (See 'Pathogenesis' below.)
AIMAH is associated with adrenal glands weighing from 24 to 500 g that contain multiple nonpigmented nodules greater than 5 mm in diameter [1-3]. The nodules appear to be typical benign adrenal nodules, but the internodular cortex may be either hyperplastic or atrophic.