Fibroblast growth factor 23 (FGF23), a bone-derived hormone, is emerging as a potential biomarker in cardiovascular disease. However, its role in transthyretin amyloid cardiomyopathy (ATTR-CM), a progressive infiltrative cardiomyopathy, remains poorly defined. This study examined the relationship between circulating FGF23 levels and cardiac and renal function markers in patients with ATTR-CM. In 114 patients with confirmed ATTR-CM, intact FGF23 levels were measured in venous ethylenediaminetetraacetic acid blood samples using a chemiluminescent immunoassay on the DiaSorin LIAISON XL system. Associations between FGF23 levels, cardiac biomarker levels, and disease severity were evaluated across FGF23 tertiles and National Amyloidosis Centre (NAC) stages. N-terminal pro–B-type natriuretic peptide (NT-proBNP) and troponin T levels were significantly associated with FGF23 tertiles. NT-proBNP medians across tertiles were 1,608, 2,920, and 1,948.5 pg/mL, respectively (P = 0.0084). Higher FGF23 levels were significantly associated with advanced NAC classification, and cumulative probability modeling supported its association with disease stage. After adjustment for eGFR, FGF23 remained significantly associated with NT-proBNP (Spearman’s ρ = 0.16; p = 0.084). However, the association with troponin T did not reach statistical significance (ρ = 0.19; p = 0.043), representing a non-significant trend. This is the first study to demonstrate a significant association between FGF23 and established markers of cardiac injury and disease staging in ATTR-CM, supporting FGF23 as a potential complementary biomarker for risk stratification.
