Low molecular weight iron dextran increases fibroblast growth factor-23 concentration, together with parathyroid hormone decrease in hemodialyzed patients.

Fibroblast growth factor (FGF)-23 inhibits PTH production. Elevated FGF-23 and parathyroid hormone (PTH) levels are characteristic of hemodialyzed patients. Iron polymaltose was shown to increase FGF-23 concentration. The effect of intravenous low molecular weight iron dextran (LMID) on these hormones and bone metabolism has not been studied in hemodialysis (HD). Twelve HD patients were prospectively followed up for 3 weeks after a single infusion of LMID. Calcium, phosphate, FGF-23, PTH, degradation products of C-terminal telopeptides of type I collagen (CTX) and procollagen I N-terminal propeptide (PINP) were measured prior to, and at week 1 and week 3 after the LMID administration. FGF-23 increased significantly from 453.4 (68.6-3971.5) pg/mL at baseline to 971.8 (779.5-3361.4) pg/mL (P = 0.001) at week 1 and started to decrease toward the initial value at week 3. The changes were accompanied by a significant decline in PTH from 367.6 (21.4-1487.4) pg/mL at baseline to 315.7 (16.4-1339.8) pg/mL (P = 0.018) at week 1 and subsequently began to increase toward the initial values. Phosphate, calcium, CTX and PINP did not change over the study course. LMID causes an increase in FGF-23 concentration together with a decrease in PTH. Our study highlights a pathophysiological element, which may connect suppression of parathyroid glands with intravenous iron supplementation.