KL and cardiac hypertrophy: Besides high FGF23 levels, klotho deficiency also seems to be associated with cardiac dysfunction in humans and rodents (25, 29, 31), and rescuing the availability of klotho by genetic overexpression or intravenous delivery of soluble klotho shows beneficial outcomes including amelioration of cardiac hypertrophy in klotho-deficient uremic mice and suppression of cardiac fibroblast activation and collagen synthesis (31–33).