Bone Abstracts

Objective: Bone is one of endocrine organ and osteocytes secretes FGF23, Sclerostin and DKK1. FGF23 inhibits renal phosphate reabsorption and suppresses 1-α hydroxylase activity. Calcitriol stimulates FGF23 synthesis in bone. We aimed to determine the effect of single bolus injection of vitamin D on serum FGF23, DKK1 and Sclerostin concentrations in vitamin D-deficient subjects.

Design and methods: The study group was composed of placebo group with severe vitamin D deficient group (n=9, 25 (OH) D=8.77±0.73, mean age 30.56±2.63 years), intervention group with severe vitamin D-deficient healthy subjects (n=10, 25(OH) D=7.56±0.48 ng/ml, mean age 31.80±2.51 years), intervention group with vitamin D-deficient healthy subjects (n=11, 25(OH) D=13.57±0.76, mean age 35.55±2.52 years). The groups were compared for serum FGF23, Sclerostin, DKK1, intact parathyroid hormone (PTH), and urinary excretion of calcium and phosphate after single injection of plain vitamin D 20,000 unit.

Results: Serum 25(OH)D was increased significantly 1, 2, 3 and 3.5 month after single bolus injection of 20,000 unit of vitamin D, however intact PTH was not changed significantly after treatment. Serum FGF23 concentrations were not significantly changed after treatment in both intervention groups. Serum FGF23 was slightly elevated in two subjects with IDA with iron replacement treatment. Serum Sclerostin was also decreased slightly after replacement, however, serum DKK1 was not changed significantly at all.

Conclusion: Single bolus injection of vitamin D does not show any significant change of serum FGF23, Sclerostin and DKK1 concentrations and it may not have unfavorable effects on bone formation and mineralization.