Effect of ferric citrate hydrate on FGF23 and PTH levels in patients with non-dialysis-dependent chronic kidney disease with normophosphatemia and iron deficiency.

Background: In patients with normophosphatemia with chronic kidney disease (CKD), fibroblast growth factor 23 (FGF23) and parathyroid hormone (PTH) increase urinary phosphate excretion while maintaining serum phosphate within the normal range. Recent reports have shown that, in this stage, phosphate binders do not decrease serum FGF23 and PTH levels. Iron deficiency promotes transcription of FGF23 and iron-supplementation for iron deficiency decreases serum FGF23 levels. We hypothesized that ferric citrate hydrate, an iron-based phosphate binder, will decrease serum FGF23 levels in patients with non-dialysis-dependent CKD with normophosphatemia and iron deficiency.

Methods: This was a single-center, randomized, open-label interventional study. The inclusion criteria were as follows: (1) eGFR < 45 mL/min/1.73 m, (2) normophosphatemia, (3) iron deficiency. Patients were assigned to the following groups: ferric citrate hydrate (FCH)-group, sodium ferrous citrate (SFC)-group, and control-group. After 12 weeks of intervention, we evaluated serum FGF23 levels and CKD-mineral bone disorder markers.

Results: There were 17 patients in the FCH-group, 14 in the SFC-group, and 9 in the control-group. The serum ferritin levels increased in the FCH-group and SFC-group compared with baseline. Serum FGF23 levels were unchanged; the change in the FCH-group was from 52.91 RU/mL (42.48-72.91) to 40.00 RU/mL (30.30-58.13) (P = 0.1764). However, in the FCH-group, serum PTH levels significantly decreased compared with baseline, from 68.00 pg/mL (49.00-141.00) to 60.00 pg/mL (44.00-144.00) (P = 0.0101).

Conclusion: Iron-based phosphate binder did not decrease serum FGF23 levels, but decreased serum PTH levels.