Background: Fibroblast growth factor 23 (FGF23) is known to cause left ventricular hypertrophy (LVH), but controversy exists concerning its effect in dialysis. This study evaluated associations between FGF23 levels, echocardiography and prognosis in patients on hemodialysis (HD). Methods: Patients >18 years on chronic HD were included in this cross-sectional study. Plasma C-terminal FGF23 concentration was measured with ELISA and transthoracic echocardiography was performed, both before and after HD treatment. Results: 239 haemodialysis (HD) patients were included in the study. The FGF23 was median 3560 RU/ml (IQR 1447-9952). The mean left ventricular mass index (LVMI) was 110.2 +/- 26.7 g/m(2) and the left ventricular ejection fraction (LVEF) was 52.7 +/- 9.9%. Defined by LVMI, LVH was found in 110 patients (46%), of which 92 (84%) had hypertension (p < 0.01) Patients with LVH had FGF23 levels of 5319 RU/ml (IQR 1858-12,859) and those without 2496 RU/ml (IQR 1141-7028) (p < 0.01). FGF23 was significant positive correlated with LVMI (p < 0.01), and negatively to LVEF (p < 0.01). In a multivariate analysis, FGF23 was correlated with LVEF (p < 0.01), but only marginally to LVMI (p < 0.01). Cardiovascular events in the follow up period was not correlated with FGF23. Furthermore, FGF23 was independently correlated with overall mortality (p < 0.001). Conclusion: FGF23 was positively correlated with LVH and negatively to LVEF. FGF23 was an independent predictor for overall mortality. (C) 2019 Sociedad Espanola de Nefrologia. Published by Elsevier Espana, S.L.U.