Effect of Vitamin D Repletion on Urinary Calcium Excretion among Kidney Stone Formers

Background and objectives Despite the important role of vitamin D in maintaining bone health, many clinicians are reluctant to treat vitamin D deficiency in kidney stone formers because of the theoretical risk of increasing urinary calcium excretion. This study examined the effect of vitamin D repletion on urinary calcium excretion among stone formers. Design, setting, participants, & measurements Participants (n=29) were recruited from urology clinics affiliated with New York Presbyterian Hospital. Enrollment criteria included a history of nephrolithiasis, urinary calcium excretion between 150 and 400 mg/d, and a serum 25-hydroxyvitamin D level < 30 ng/ml. Participants were given oral ergocalciferol (50,000 IU/wk) for 8 weeks. Serum and 24-hour urine tests were repeated after 8 weeks. Results Levels of 25-hyd roxyvitamin D increased significantly after vitamin D repletion (17 +/- 6 and 35 +/- 10 ng/ml, P < 0.001), but mean 24-hour urinary calcium excretion did not change (257 +/- 54 and 255 +/- 88 mg/d at baseline and follow-up, respectively, P=0.91). However, 11 participants had an increase in urinary calcium excretion >= 20 mg/d; these participants also had an increase in urine sodium excretion, likely reflecting dietary variability. No participant experienced adverse effects from vitamin D, including hypercalcemia. Conclusions Among stone formers with vitamin D deficiency, a limited course of vitamin D repletion does not seem to increase mean urinary calcium excretion, although a subset of individuals may have an increase. These data suggest that vitamin D therapy, if indicated, should not be withheld solely on the basis of stone disease, but 24-hour urinary calcium excretion should be monitored after repletion. Clin J Am Soc Nephrol 7: 829-834, 2012. doi: 10.2215/CJN.11331111