FGF23 and rickets: In vitamin D-replete Gambian children, rickets was associated with elevated plasma concentrations of total-FGF23 (as measured by an assay which detects both the intact hormone and the C-terminal fragments that result from its cleavage), 1,25(OH)2D, and total alkaline phosphatase (a marker of dysregulated bone formation that is elevated in rickets and osteomalacia) and with lower plasma concentrations of phosphate (3).