LRP2 and chronic kidney disease: The decreased concentration of circulating 25(OH)2-vitamin D was attributed to lack of dietary intake of vitamin D and to increased urinary losses;154 increased urinary losses of the complex of calcidiol with VDBP may be explained by the lack of megalin expression in renal tubules during CKD (Figure 9).155 Circulating calcidiol and calcitriol are largely bound to VDBP.