Antiproteinuric treatment reduces urinary loss of vitamin D-binding protein but does not affect vitamin D status in patients with chronic kidney disease.

Vitamin D deficiency is common in chronic kidney disease (CKD). Increased urinary loss of vitamin D binding protein (VDBP), the main transporter of 25-hydroxyvitamin D(3) in the circulation, has been postulated to contribute to vitamin D deficiency in proteinuria. To test this hypothesis we analyzed urinary and plasma levels of VDBP, 25-hydroxyvitamin D(3) and 1,25-dihydroxyvitamin D(3) from proteinuric patients, before and after antiproteinuric interventions.