FGF23 and chronic kidney disease: In the setting of CKD, these elevations in PTH are part of an adaptive process that gradually become maladaptive in response to declining kidney function, causing abnormalities in several biochemical parameters including impaired phosphate excretion, increased FGF-23, hypocalcaemia and failure to bioactivate vitamin D; the combined effect of these multiple pathways is to promote the progression of SHPT as detailed in Fig. 2 [6].