Decreased Klotho concentration is associated with a higher risk of HF and is confirmed by our observations in ERI group (patients with HF) and in CHF patients from the Frankfurt Bone Marrow-Derived Cell Therapy Registry which had a lower serum Klotho concentration than controls (the median serum Klotho concentration was 674 pg/mL in CHF patients and 903 pg/mL in controls; IBL International ELISA kit) (von Jeinsen et al., 2019). Here, KL is linked to hydrops fetalis.