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Vitamin D repletion does not increase urine calcium in patients with vitamin D defficiency
Brian H. Eisner, MD, Sherri-Ann Burnett-Bowie, MD.
Massachusetts General Hospital, Boston, MA, USA.

BACKGROUND: Vitamin D is known to increase intestinal calcium absorption. Theoretically, vitamin D supplementation could lead to increases in urine calcium and therefore increase risk of calcium nephrolithiasis. We examined changes in urinary calcium in patients with Vitamin D deficiency who underwent vitamin D repletion over a 12 week period.
METHODS: We performed an IRB approved, randomized, placebo-controlled 12-week study. Inclusion criteria included age 18-45 years, serum 25-OHD < 20 ng/ml, regular menses or OCP use (females), serum testosterone > 270 ng/ml (men), and no history of kidney stones. Patients were randomized to the control group (placebo every week) or the intervention group (50,000 IU Vitamin D every week) for 12 weeks. All subjects (control and intervention) received 1000 to1500 mg/d of calcium from diet or supplements. Serum studies (phosphate, calcium, creatinine, PTH, 25-OHD, and 1,25 OHD) and fasting urine studies (spot calcium, spot creatinine) were performed at enrollment and after 12 weeks of vitamin D repletion. Statistical analyses were performed using univariate analysis, age-adjusted linear regression, and multivariate linear regression (adjusted for age, gender, body mass index, and race).
RESULTS: From enrollment to week 12, there was a small increase in serum 25-OHD in the control group (14.7 ng/ml to 17.7 ng/ml, p=0.03) and a substantial increase in the intervention group (14.3 ng/ml to 45.8 ng/ml, p < 0.0001). Over the 12 week treatment period, on univariate analysis, there was no change in spot urine calcium:creatinine (Ca:Cr) ratio for the control group (6.16 to 6.52, p=0.68) or the intervention group (5.36 to 6.80, p=0.10). On age-adjusted linear regression, Vitamin D repletion was not associated with a change in urine Ca:Cr ratio (ß = -0.51, 95% CI -1.74 to 0.71). On multivariate linear regression, Vitamin D repletion was not associated with a change in urine Ca:Cr ratio (ß = -0.59, 95% CI -1.84 to 0.67).
CONCLUSIONS: In this 12-week study, Vitamin D repletion did not increase urine Ca:Cr ratio. Vitamin D repletion, in the short term, does not appear to increase the risk of hypercalciuria in patients with Vitamin D deficiency.


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