ACTH-dependent hyperfunction may result from Hypersecretion of ACTH by the pituitary gland (Cushing disease) Secretion of ACTH by a nonpituitary tumor, such as small cell carcinoma of the lung or a carcinoid tumor (ectopic ACTH syndrome) Administration of exogenous ACTH ACTH-independent hyperfunction usually results from Therapeutic administration of corticosteroids Adrenal adenomas or carcinomas Rare causes of ACTH-independent hyperfunction include primary pigmented nodular adrenal dysplasia (usually in adolescents) and bilateral macronodular hyperplasia (in older patients).