KL and chronic kidney disease: It has been shown that serum α-Klotho starts to decline in stage 2 CKD, and urinary α-Klotho even earlier, in stage 1 CKD [90], and for each 1 ml/min/1.73m2 eGFR decrease, an adjusted mean decrease of 3.2 pg/ml of serum α-Klotho was revealed [91].