Background: Secondary hyperparathyroidism is a common complication in patients with stage 5 chronic kidney disease (CKD), accelerated by hyperphosphatemia. Fibroblast growth factor 23 (FGF-23), a phosphorus-regulating protein, has key roles in several phosphate-wasting disorders. The aim of this study is to examine the association of advanced secondary hyperparathyroidism with circulating FGF-23 levels.
Methods: Fifteen patients with marked secondary hyperparathyroidism (parathyroid hormone [PTH], 990 +/- 118 pg/mL [ng/L]) were enrolled. All underwent parathyroidectomy with forearm autotransplantation (PTX), and their FGF-23 levels were measured before and after PTX (days 1, 3, 7, and 10) by means of sandwich enzyme-linked immunosorbent assay.
Results: Preoperative FGF-23 levels correlated positively with phosphorus (P < 0.05), calcium-phosphorus product (Ca x P; P < 0.0005), and PTH values (P < 0.05). Serum FGF-23 levels decreased time dependently after PTX (P < 0.0005). Both serum phosphorus and Ca x P values decreased similarly after PTX ( P = 0.0001). Furthermore, FGF-23 levels days 1 and 3 correlated linearly with serum phosphorus (P < 0.05; P < 0.005, respectively) and Ca x P values (P < 0.01; P < 0.0001, respectively).
Conclusion: FGF-23 levels correlate positively with serum phosphorus, Ca x P, and PTH values in patients with advanced secondary hyperparathyroidism. Complete ablation of progressive parathyroid glands reduces circulating FGF-23 levels, simultaneously decreasing serum phosphorus and Ca x P values. These findings suggest that hyperplastic parathyroid glands, together with hyperphosphatemia, affect abnormal FGF-23 metabolism in patients with stage 5 CKD with advanced secondary hyperparathyroidism.