FKBP5 and Cushing syndrome due to macronodular adrenal hyperplasia: Although the expression levels of FKBP4 and FKBP5 in corticotroph tumors have not been determined, reduced leukocyte DNA methylation of FKBP5 [42] and increased FKBP5 mRNA levels in blood [43] have been found in patients with Cushing’s syndrome.