FGF23 and chronic kidney disease: FGF-23 signalling requires the presence of the coreceptor Klotho.S40 CKD is characterised by Klotho deficiency and increased FGF-23 levels, which are independently associated with cardiovascular mortality.S41 In mouse models of Klotho deficiency, an accelerated ageing syndrome results with vascular calcification that resembles features of uraemia.S42