RT Journal Article SR Electronic T1 Effect of Calcitriol on FGF23 Level in Healthy Adults and its Dependence on Phosphate Level JF In Vivo JO In Vivo FD International Institute of Anticancer Research SP 145 OP 150 VO 31 IS 1 A1 EFFROSYNI GEORGIADOU A1 HELEN MARKETOU A1 GEORGE TROVAS A1 ISMENE DONTAS A1 NIKOLAOS PAPAIOANNOU A1 KONSTANTINOS MAKRIS A1 ANTONIOS GALANOS A1 ATHANASIOS G. PAPAVASSILIOU YR 2017 UL http://iv.iiarjournals.org/content/31/1/145.abstract AB Aim: To evaluate the short-term effects of calcitriol and sevelamer hydrochloride on fibroblast growth factor-23 (FGF23) in humans and to determine whether the effect is direct or indirect through calcitriol-induced increased absorption of phosphorus from the intestine. Patients and Methods: A total of 15 healthy individuals were tested at three time points and stages, for 24 h and at 1-week intervals. During each stage, blood samples were taken at three time points (0, 8 and 24 h); baseline stage: under no intervention; second stage, while receiving 0.5 μg calcitriol orally twice daily; and at the third stage, while receiving 0.5 μg calcitriol orally twice daily and sevelamer hydrochloride during meals. The changes in FGF23, parathyroid hormone, calcitriol, Ca, and phosphorus were determined. Results: During calcitriol administration, the FGF23 level changed significantly (p=0.008), with the level at 24 h levels being significantly higher than at 8 h (8.8 pg/ml vs. 13.0 pg/ml, p=0.036). There was a statistically significant difference in the percentage change, among the three stages, at time 8 to 24 h and 0 to 24 h for FGF23 (p=0.014 and p=0.015, respectively), with significant differences between baseline vs. calcitriol for 8 to 24 h FGF23 change (−9.23% vs. 26.98%, p=0.003) and a trend between baseline vs. calcitriol (p=0.061) and calcitriol plus sevelamer (p=0.069) for 0 to 24 h FGF23 change. Conclusion: Administration of calcitriol to healthy individuals increases the circulating level of FGF23 within 24 h. Combined calcitriol and sevelamer administration restrains the increase of FGF23, suggesting that calcitriol-induced increased absorption of phosphate from the intestine might also be involved in the increase of FGF23.