Fibroblast growth factor (FGF)-23 in patients with primary hyperparathyroidism

Objective: We aimed to determine the serum level of fibroblast growth factor-23 (FGF-23) in patients with primary hyperparathyroidism (pHPT) to understand its physiological role in the disorder. Patients and methods: Ninety-eight patients with pHPT who underwent parathyroidectomy formed the study group. We also measured serum FGF-23 in 11 of these patients on postoperative day 6. Results: Serum FGF-23 levels was significantly higher in pHPT patients than in healthy controls (35.6+/-17.8 ng/l vs 28.9+/-11.2 ng/l (mean+/-S.D.); P < 0.001 (Pearson's correlation coefficient)). but there was no significant difference in the serum FGF-23 level between pHPT patients with normal renal function (creatinine clearance (Ccr) of greater than or equal to70 ml/min) and healthy controls. Serum FGF-23 correlated positively with serum calcium (P < 0.0001) and intact parathyroid hormone (PTH) (P < 0.01), and negatively with Ccr (P < 0.001), serum phosphate (P < 0.05), and serum 1.25-dihydroxyvitamin D (1,25(OH)(2)D) (P < 0.05). Multiple linear regression analysis of factors potentially determining serum FGF-23 levels in pHPT patients showed serum calcium (P < 0.01) and Ccr (P < 0.001) to be significant predictors. The serum levels of FGF-23 did not change after parathyroidectomy despite the normalization of serum calcium values. Multiple linear regression anaysis revealed that serum FGF-23 was not a significant predictor of serum phosphate or 1,25(OH)2D in pHPT patients. Conclusions: FGF-23 may not play a significant role in regulating phosphate or 1,25(OH)(2)D in pHPT patients, especially in those with normal renal function. Further studies are warranted to determine the role of FGF-23 in renal insufficiency or failure.