We have now clearly demonstrated that salivary cortisol is a useful surrogate for plasma cortisol in ESRD patients in agreement with many previous studies of patients with Cushing's syndrome, hypoalbuminemia, corticosteroid-binding globulin mutations, and adrenal insufficiency (6, 7, 18, 19). This evidence concerns the gene SERPINA6 and Cushing syndrome due to macronodular adrenal hyperplasia.