Prevalence of FGF23 elevation in patients with hypophosphatemia.

BACKGROUND AND AIMS: To investigate the contribution of FGF23 in explaining the cases of hypophosphatemia observed in clinical practice, we aimed to determine for the first time the prevalence of FGF23 elevation in patients with hypophosphatemia and to describe the different mechanisms of FGF23-related hypophosphatemic disorders.

MATERIALS AND METHODS: We performed a prospective, observational, multicenter, cohort study of 260 patients with hypophosphatemia. Blood measurements (PTH, 1,25-dihydroxyvitamin D, bone alkaline phosphatase, 25-hydroxyvitamin D, and FGF23) were performed on a Liaison XL® (DiaSorin) analyzer.

RESULTS: Primary elevation of FGF23 (> 95.4 pg/mL) was reported in 10.4% (95CI: 7.0-14.7) of patients (n=27) with hypophosphatemia, suggesting that at least 1 in 10 cases of hypophosphatemia was erroneously attributed to an etiology other than FGF23 elevation. Patients with elevated blood FGF23 were grouped according to the etiology of the FGF23 elevation. Thus, 10 patients had a renal pathology, chronic kidney disease or post-renal transplantation condition. The remaining patients (n=17) had the following etiologies: malignancies (n=9), benign pancreatic tumor (n=1), post-cardiac surgery (n=4), cirrhosis (n=2), and chronic obstructive pulmonary disease (n=1).

CONCLUSION: In order to improve patient management, it seems essential to better integrate plasma FGF23 measurement into the routine evaluation of hypophosphatemia.