KL and chronic kidney disease: However, as well investigated by Scholze A. et al., CKD patients with s-klotho below 204 pg/mL had higher age, lower phosphate clearance, and lower bone-specific alkaline phosphatase, indicating that older age more than CKD stage can affect the s-Klotho concentration and function (reference Klotho level in normal adults from 239 to 1266 pg/mL) [92].