Szeto CC et al. (2008) Oral calcitriol for the treatment of persistent proteinuria in immunoglobulin A nephropathy: an uncontrolled trial. Am J Kidney Dis 51: 724–731

Although angiotensin-converting-enzyme inhibitors and angiotensin-receptor blockers can slow deterioration of renal function in patients with IgA nephropathy, these drugs do not address the inflammatory component of the disease. Calcitriol (1,25-dihydroxyvitamin D3) has been reported to reduce progressive glomerular damage in subtotally nephrectomized rats. In an open-label, uncontrolled trial, Szeto et al. examined the antiproteinuric effect of calcitriol in 10 patients who had biopsy-proven IgA nephropathy and persistent proteinuria of more than 1 g/day (or urine protein to creatinine ratio >1 g/g) despite use of an angiotensin-converting-enzyme inhibitor or angiotensin-receptor blocker for at least 6 months.

All patients received calcitriol 0.5 µg twice weekly for up to 12 weeks and were followed up at weeks 2, 4, 6, 8 and 12. The dose was reduced if serum corrected calcium level exceeded 2.55 mmol/l (10.2 mg/dl). Urinary protein to creatinine ratio declined from 1.98 ± 0.74 g/g at baseline to 1.48 ± 0.81 g/g at 6 weeks (P <0.001), and the ratio remained lower than at baseline at 12 weeks (P = 0.004). No significant changes in blood pressure or renal function were noted during follow-up. Hypercalcemia was observed in one patient but resolved on reduction of the calcitriol dose to 0.25 µg twice per week.

On the basis of these results, the authors conclude that further studies of the effect of calcitriol on persistent proteinuria are warranted. They estimate that a randomized controlled 1-year trial in 156 patients (78 per arm) would have sufficient statistical power to detect a significant effect.