Fibroblast growth factor 23, parathyroid hormone, and 1α,25- dihydroxyvitamin D in surgically treated primary hyperparathyroidism

OBJECTIVE: To determine whether fibroblast growth factor 23 (FGF23) contributes to the hypophosphatemia of primary hyperparathyroidism. PATIENTS AND METHODS: Thirteen adult patients with primary hyperparathyroidism had serum collected before and after parathyroidectomy for analysis of inorganic phosphorus, calcium, 1α,25-dihydroxyvitamin D (1α,2B[OH] ₂D), parathyroid hormone (PTH), FGF23, creatinine, and bone-specific alkaline phosphatase (BSAP). Patients were recruited between July 24, 2003, and February 11, 2004. RESULTS: Before surgery, patients had elevated serum calcium and PTH concentrations. Serum phosphorus concentrations were In the low-normal range. The FGF23 concentrations were not elevated in patients with primary hyperparathyroidism compared with healthy contrals. Within 24 hours of surgery, serum calcium, FFH, 1α,25(OH)₂D, and BSAP concentrations were lower (P<.002 for all) and phosphorus concentrations were higher (P=.003) than in the preoperative state. The FGF23 concentrations were similar 1 day and 6 weeks after surgery. The FGF23 concentrations did not correlate with serum phosphorus, calcium, PTH, 1α,25(OH)₂D, creatinine, or BSAP concentrations in the preoperative or postoperative state. CONCLUSION: Parathyroid hormone is the major regulator of serum phosphorus concentrations in patients with primary hyerparathyroidism. Fibroblast growth factor 23 does not appear to play a role in phosphorus homeostasis in patients with surgically treated primary hyperparathyroidism.