Serum FGF-23 level was found to be the most useful factor in predicting future development of refractory secondary hyperparathyroidism in long-term dialysis patients with mild secondary hyperparathyroidism. The measurement of serum FGF-23 levels is a promising laboratory examination that can be applied in the clinical practice of uremic secondary hyperparathyroidism.

Background and objectives: Cinacalcet is effective in reducing serum parathyroid hormone (PTH) in patients with secondary hyperparathyroidism. However, it has not been proven whether parathyroid gland size predicts response to therapy and whether cinacalcet is capable of inducing a reduction in parathyroid volume.Design, setting, participants, & measurements: This 52-week, multicenter, open-label study enrolled hemodialysis patients with moderate to severe secondary hyperparathyroidism (intact PTH >300 pg/ml). Doses of cinacalcet were adjusted between 25 and 100 mg to achieve intact PTH <180 pg/ml. Ultrasonography was performed to measure the parathyroid gland size at baseline, week 26, and week 52. Findings were also compared with those of historical controls.Results: Of the 81 subjects enrolled, 56 had parathyroid glands smaller than 500 mm 3 (group S) and 25 had at least one enlarged gland larger than 500 mm 3 (group L). Treatment with cinacalcet effectively decreased intact PTH by 55% from baseline in group S and by 58% in group L. A slightly greater proportion of patients in group S versus group L achieved an intact PTH <180 pg/ml (46 versus 32%) and a >30% reduction from baseline (88 versus 78%), but this was not statistically significant. Cinacalcet therapy also resulted in a significant reduction in parathyroid gland volume regardless of pretreatment size, which was in sharp contrast to historical controls (n ‫؍‬ 87) where parathyroid gland volume progressively increased with traditional therapy alone.Conclusions: Cinacalcet effectively decreases serum PTH levels and concomitantly reduces parathyroid gland volume, even in patients with marked parathyroid hyperplasia.

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.

Cinacalcet lowers serum FGF23 in haemodialysis patients with SHPT independently of the effects of active vitamin D. Pretreatment FGF23 cannot predict treatment response to cinacalcet in this setting. The precise mechanism of FGF23 reduction by cinacalcet and its clinical impact on outcomes in patients remain to be investigated.

Background/Aims: Fibroblast growth factor-23 (FGF-23) is a recently discovered phosphaturic factor. Although increased levels of serum FGF-23 have been reported in dialysis patients, the role of high FGF-23 levels remains unclear. Since FGF-23 is associated also with vitamin D metabolism, we examined the changes of serum FGF-23 levels in chronic dialysis patients treated with intravenous calcitriol therapy. Methods: Thirty patients with severe secondary hyperparathyroidism were treated with intravenous calcitriol (0.5–1.0 µg) two or three times per week for 6 months. The changes of serum levels of calcium, phosphate, intact PTH, and FGF-23 were evaluated. Results: Baseline serum FGF-23 levels were markedly high. By intravenous calcitriol therapy, intact PTH levels decreased effectively in the first month (p < 0.001). In contrast, FGF-23 levels increased gradually during the study period (p = 0.027). The Δ serum FGF-23 level was significantly correlated with the total doses of calcitriol injected intravenously in 6 months in patients with refractory secondary hyperparathyroidism (R^{2 =} 0.147; p = 0.036). Conclusions: Intravenous calcitriol decreased serum intact PTH level and increased serum FGF-23 levels significantly. Extremely high levels of serum FGF-23 in these patients may be attributed, at least in part, to the cumulative dose of vitamin D.