Fibroblast Growth Factor 23 (FGF23) and Klotho Protein in Beta-Thalassemia

Derangements in phosphate and calcium homeostasis are common in patients with beta-thalassemia. Fibroblast growth factor 23 (FGF23) is among the main hormones regulating phosphate levels, while several studies underline an interplay between iron (Fe) and FGF23. Herein, we investigated, for the first time, the serum intact molecule (iFGF23) and the carboxyl-terminal fragment (C-FGF23) and Klotho levels simultaneously in patients with beta-thalassemia major receiving iron chelation regimens in comparison to healthy control subjects. We also correlated them with the body iron burden. The observational case-control study included 81 subjects (40 thalassemic patients and 41 healthy controls). Serum iFGF23, C-FGF23 and Κlotho were measured by ELISA. Parathormone, 25-hydroxycholecalciferol, calcium, and phosphorus were measured in blood and/or urine. The degree of hemosiderosis was evaluated by assessing the serum ferritin levels and performing T2* MRI measurements. Serum C-FGF23 levels were significantly lower in patients compared to control subjects (p=0.04), while iFGF23 and Klotho levels did not differ. Serum C-FGF23 levels were negatively correlated with ferritin (r=-0,421, p=0.018), whereas there were no significant correlations of each of the three factors with the iron chelation therapy. Decreased serum C-FGF23 levels were found in βTh patients which may be attributed to inhibition of proteolytic cleavage of iFGF23. Further studies in a greater number of patients will shed more light on the disturbances of the iFGF23, Klotho and C-FGF23 in thalassemia and their possible role in bone disease of such patients.