FGF23 works in close synergy with α-Klotho, a multifunctional protein that is predominantly expressed in kidney tubular epithelium and is also implicated in the metabolism of phosphate, calcium and Vitamin D. In the study of Ozeki et al. [101] on a cohort of cardiac patients with CKD, estimated glomerular filtration rate (eGFR) was correlated negatively with FGF23 and positively with α-Klotho serum levels. Here, FGF23 is linked to chronic kidney disease.