However, previous findings demonstrating that the renal Klotho expression levels in patients with CKD are as low as 5% of those observed in persons with normal kidney function [37] led us to consider that serum sKlotho levels appear to be disproportionately high in chronic HD patients, including our study population possibly due to extrarenal production or impaired metabolic clearance of sKlotho, or some combination of the two. This evidence concerns the gene KL and chronic kidney disease.