Oral iron supplementation with sodium ferrous citrate reduces the serum intact and c-terminal fibroblast growth factor 23 levels of maintenance haemodialysis patients

Abstract

Aim: Iron deficiency stimulates fibroblast growth factor 23 (FGF23) transcription. This study aimed to determine whether oral ferrous iron (Fe²⁺ ) reduces the serum FGF23 levels of iron-deficient maintenance haemodialysis (MHD) patients in the same way as oral ferric iron (Fe³⁺ ) METHODS: Thirty-one MHD patients with iron deficiency were enrolled in this prospective study. Patients who had taken iron supplements during the 8 weeks before the study were excluded. The patients' iron stores and their serum FGF23, phosphate, intact parathyroid hormone (iPTH), albumin, C-reactive protein (CRP), and albumin-adjusted calcium (Ca) levels were examined at the baseline and after 3 months' treatment with sodium ferrous citrate (Fe²⁺ ).

Results: The patients' transferrin saturation values and serum iron and ferritin levels were significantly increased after 3 months' treatment (P < 0.01), as were their serum albumin levels (P < 0.05). Conversely, their serum intact FGF23 (iFGF23) [1820 (342-4370) vs 1240 (214-2940) pg/mL, P < 0.05], C-terminal FGF23 (cFGF23) [309 (120-1211) vs 259 (99-600) pg/mL, P < 0.05)], and CRP levels (P < 0.01) were significantly reduced after 3 months' treatment. No changes were detected in the patients' serum iFGF23:cFGF23 ratios or their serum phosphate, Ca, or iPTH levels. The changes in the patients' serum iFGF23 and cFGF23 levels induced by sodium ferrous citrate supplementation were shown to be attributable to changes in their serum ferritin levels (P < 0.05).

Conclusion: Short-term oral iron supplementation with sodium ferrous citrate replenished the iron stores and reduced the serum iFGF23 and cFGF23 levels of MHD patients with iron deficiency without affecting their serum phosphate, Ca, or iPTH levels.

Keywords: bone metabolism; haemodialysis; iron.

Figure 1

Subjects’ transferrin saturation (TSAT) values and serum iron and ferritin levels at the baseline and after 3 months’ sodium ferrous citrate treatment. Data are expressed as mean ± standard deviation values. *P < 0.01, ** P < 0.0001 compared with the baseline values.

Figure 2

Subjects’ serum intact FGF23 and C‐terminal FGF23 levels and intact FGF23:C‐terminal FGF23 ratios at the baseline and after 3 months’ sodium ferrous citrate treatment. The iFGF23 (pg/mL) and cFGF23 (pmol/L) measurements were obtained simultaneously, and the unit conversion of the cFGF23 data was performed using the following equation: 0.133 pmol/L = 1 pg/mL. The data are expressed as median values and interquartile ranges. *P < 0.05 compared with the baseline values.