The speculated mechanism is that aldosterone is co-expressed with the enzyme 11β-hydroxysteroid dehydrogenase II (11β-HSC2) and cortisol is converted to cortisone, which cannot activate the MRs.30,31 However, in HF patients, 11β-HSC2 may be downregulated, causing cortisol to activate the MR. This evidence concerns the gene NR3C2 and hydrops fetalis.