FGF-23, Klotho and Vitamin D Levels in Scleroderma

BACKGROUND Scleroderma is a chronic connective tissue disease of unknown etiology. Vitamin D and parathyroid hormone (PTH) that play particular functions in calcium and phosphate homeostasis may be involved in the etiology of this disorder. Klotho, the co-receptor of the fibroblast growth factor 23 (FGF-23), can interfere with calcium and phosphate metabolism. The purpose of this study was to evaluate serum Klotho, FGF-23, intact PTH (iPTH) and vitamin D levels in scleroderma patients compared with the healthy controls. METHODS The study was performed in Biotechnology Research Center, Tabriz University of Medical Sciences (TUMS) from 2014-2015. Sixty scleroderma patients based on the classification criteria of systemic sclerosis and 30 age- and sex-matched healthy controls were included in this study. Serum Klotho, FGF-23, 25-hydroxy vitamin D (25-OH Vit D), and iPTH levels were analyzed using ELISA. RESULTS Serum levels of Klotho and 25-OH Vit D in the scleroderma patients were lower than those in the healthy controls (P<0.001). In addition, scleroderma patients had higher serum iPTH levels than the controls (P<0.001). There was no significant difference in serum FGF-23 levels between the patients and controls (P=0.202). CONCLUSION The decreased serum Klotho, 25-OH Vit D, and increased iPTH levels in the scleroderma patients may be associated with the pathogenesis of this disease and could be considered a future therapeutic target.