Fibroblast growth factor 23 in acute burn patients: Novel insights from an intact-form assay

• Two different assays are currently available to quantify circulating FGF23.
• Burn injury is associated with a disrupted balance between production and cleavage.
• Thus, in burn patients, there is a dissociation between c-terminal FGF23 and iFGF23.
• Role of inflammation and low iron levels in FGF23 regulation need to be explored.
• These results rule out FGF23 as one of the causes of burn-related hypophosphatemia.

IntroductionFibroblast growth factor 23 (FGF23) is a key regulator in phosphate and vitamin D metabolism When measured with c-terminal assay, it has been shown to be increased following burn. Progress in understanding FGF23 physiology has emphasized the importance of assessing the intact form of FGF23.MethodsThe present cohort study is a complementary analysis of a previously published work. Patients >18 years, admitted within 24 h after injury with burn surface area (BSA) >10% were included. C-terminal (c-term) and intact (i) FGF23 assay were performed at admission and every week during 4 weeks of follow-up. Inflammation and iron status were assessed at the same time points.ResultsTwenty patients were initially included and 12 were followed until day 28. The c-term FGF23 tended to gradually increase during the 4 weeks of follow-up while iFGF23 was quite stable into normal ranges. Iron status showed a typical inflammatory profile. C-term FGF23 was significantly positively correlated with c-reactive protein (CRP) and negatively correlated with iron levels. iFGF23 was not correlated with CRP or iron.ConclusionFGF23 status following burn is characterized by a dissociation between c-term FGF23 and iFGF23. The hypothesis of an increased cleavage may be raised. Respective role of inflammation and iron levels in such deregulation need to be specified. Both c-term and intact assays should be performed in further studies aiming to increase knowledge on FGF23 regulation and effects in burn patients.