This assay helps identify the cause of hypocortisolism and hypercortisolism. In hypocortisolism, elevated ACTH suggests primary adrenal insufficiency, while normal levels point to secondary insufficiency due to pituitary or hypothalamic issues. In hypercortisolism (Cushing's syndrome), a suppressed ACTH level indicates cortisol-producing adrenal adenoma/carcinoma, primary adrenal micronodular hyperplasia, or exogenous corticosteroid use.