FGF-23 Links Kidney Disease to Heart Failure Through a Hidden Hormonal Pathway

Chronic kidney disease affects hundreds of millions globally and dramatically amplifies cardiovascular risk—far beyond what blood pressure, cholesterol, or diabetes alone can explain. Researchers have long suspected that non-traditional, hormone-driven mechanisms must be involved. This review positions FGF-23 as a central culprit in that gap.

FGF-23 is produced by bone cells to regulate phosphate excretion and suppress vitamin D activation. In healthy kidneys, it acts through a co-receptor called α-Klotho paired with FGFR1c to keep mineral metabolism in balance. As kidney function declines, FGF-23 levels rise dramatically—often years before other markers of CKD progression.

The cardiac danger emerges when FGF-23 concentrations become pathologically high. At those levels, FGF-23 bypasses the Klotho-dependent pathway and instead activates FGFR4 receptors directly in cardiomyocytes. This triggers downstream signaling cascades that cause left ventricular hypertrophy, interstitial fibrosis, diastolic dysfunction, and electrophysiological remodeling—a mechanistic chain linking kidney disease to heart disease through an endocrine route.

Cohort data consistently show that elevated FGF-23 independently predicts left ventricular hypertrophy, heart failure with preserved ejection fraction (HFpEF), atrial fibrillation, and all-cause mortality—even in populations without CKD. This broadens FGF-23's relevance as a cardiovascular biomarker beyond the nephrology clinic.

Despite this compelling biology, translating FGF-23 into clinical practice remains difficult. Assay types (intact vs. C-terminal) yield different values, standardized cut-offs do not exist, and no randomized trial has yet demonstrated that interventions specifically targeting FGF-23 or the FGF-23–Klotho–FGFR axis improve hard cardiovascular outcomes. Emerging therapies targeting this axis hold promise but require rigorous validation.