A decrease in serum 1,25(OH)2D after elective hip replacement and during bone healing is associated with changes in serum iron and plasma FGF23

Objective Although calcitriol is essential for bone healing, its serum concentrations are low after hip surgery, and they continue to decline during bone healing. This study aimed to test the hypothesis of an association of changes in calcitriol production with the status of fibroblast growth factor 23 (FGF23) and iron deficiency after elective hip replacement for coxarthrosis. Methods In this prospective study, we measured the biomarkers of 17 patients undergoing elective hip replacement on admission, on the first day after surgery, and at the regular check-up after 48 ± 8 days. The serum concentrations of 25-hydroxyvitamin D, 1,25-dihydroxyvitamin D, transferrin, ferritin, parathyroid hormone, intact plasma FGF23 (iFGF23) and C-terminal FGF23 (cFGF23) were determined. Results In our patients who underwent elective hip replacement, significant correlations existed between the percent change in the conversion rate of 25(OH)D to 1,25(OH) 2 D, plasma intact to C-terminal FGF23 ratio, and serum iron. Conclusions The production of calcitriol is compromised after elective hip replacement surgery, leading to reduced levels of active vitamin D in the serum. Significant correlations between the percent change in the conversion rate of 25(OH)D to 1,25(OH) 2 D, plasma intact to C-terminal FGF23 ratio, and serum iron on the first day as well as 7 weeks after surgery could inspire future studies to determine whether and how calcitriol deficiency should be corrected, especially in fracture cases.