Molecular pathophysiology of chronic kidney disease–mineral and bone disorder: Focus on the fibroblast growth factor 23–Klotho axis and bone turnover dynamics

Chronic kidney disease-mineral and bone disorder (CKD-MBD) is a major complication of chronic kidney disease (CKD), characterized by disruptions in mineral metabolism, abnormal bone turnover and vascular calcification, which collectively increase the risk of fractures and cardiovascular disease. This review examines the molecular mechanisms underlying CKD-MBD, with a particular focus on the fibroblast growth factor 23 (FGF23)-Klotho axis - a key regulator of phosphate balance, vitamin D activation and parathyroid hormone secretion. In CKD, elevated FGF23 levels and reduced Klotho expression contribute to mineral homeostasis disturbances and bone abnormalities. The dysregulation of this pathway plays a central role in CKD-MBD pathophysiology and its associated complications. Emerging therapies, such as anti-FGF23 antibodies and recombinant Klotho, hold promise for modulating FGF23 activity and restoring mineral balance. This review highlights the importance of individualized treatment strategies based on bone turnover patterns and FGF23-Klotho axis dysfunction. Advancing our understanding of these molecular mechanisms will aid in the development of more effective diagnostic tools and therapeutic interventions to improve CKD-MBD outcomes.