Vitamin D deficiency is prevalent among idiopathic stone formers, but does correction pose any risk?

Abstract

While vitamin D (vitD) deficiency is thought to contribute to poor health in a variety of ways and should be corrected, there is still concern about giving vitD supplements to patients with a history of nephrolithiasis. The aim is to study the prevalence of vitD deficiency and the effect on stone risk of cholecalciferol (vitD3) supplementation in a cohort of idiopathic stone formers (ISF). We screened for vitD deficiency and urinary measures of stone risk, comparing vitD deficient (serum 25-OH vitD ≤30 nmol/L; ≤12 ng/mL) with vitD insufficient (31–75 nmol/L; 13–30 ng/mL) or vitD replete (>75 nmol/L; >30 ng/mL); we investigated the effect of giving vitD3 (20,000 IU orally, weekly for 4 months) to 37 of the vitD deficients. Thirty-one percent (142/456) were vitD deficient, 57% (259/456) vitD insufficient, and the rest (12%) vitD replete (55/456). Comparison among the groups showed that baseline 24-h urinary measures related to stone risk expressed as concentration ratios over urine creatinine (Cr), such as U. Calcium/Cr, U. Oxalate/Cr, U. Citrate/Cr, and U. Uric acid/Cr were not significantly different. VitD3 supplementation did significantly increase serum 25-OH vitD levels and U. Phosphate/Cr ratios, as well as reduce serum parathyroid hormone (PTH) concentrations. Following vitD3 supplementation, there was an overall rise in 24-h urine calcium excretion, but it failed to reach statistical significance (p = 0.06). U. Calcium/Cr increased in 22 out of 37 patients (average increase +0.07 mmol/mmol), decreased in 14 (average decrease −0.13 mmol/mmol), and remained unchanged in 1; 6 out of 26 initially normocalciuric ISF developed hypercalciuria; and 6 out of 9 patients who became vitD replete were hypercalciuric after supplementation. It is appropriate to monitor urinary Ca excretion in vitD-supplemented stone formers, because it may reveal underlying hypercalciuria in some treated patients.

Vitamin D, Hypercalciuria and Kidney Stones

“…Since vitamin D may increase kidney stone formation through an increase in urine calcium excretion, the evaluation of urinary calcium excretion after vitamin D supplementation is a major concern. Only two studies investigated the effect of nutritional vitamin D on urinary calcium excretion on a prospective basis [ 70 , 71 ]. Leaf et al prescribed ergocalciferol to 29 stone formers with relatively low 25-hydroxyvitamin D serum levels at baseline and concluded that a limited course of vitamin D repletion does not aggravate the mean urinary calcium excretion, although a subset of individuals may have an increase [ 70 ].…”

Medical therapy for nephrolithiasis: State of the art

“…However, a recent small RCT comparing 6 weeks of low (1 000 IU/day) versus high (50 000 IU weekly) dose vitamin D supplementation among 21 vitamin D deficient stone formers found no significant change in urinary calcium after treatment in either group, although only the higher dose group showed a significant increase in serum vitamin D levels [51] . If vitamin D repletion is indicated, urine calcium should be monitored with 24 h urine studies [52] , [53] .…”

Association between Circulating Vitamin D Level and Urolithiasis: A Systematic Review and Meta-Analysis

“…Although Reid and colleagues’ study challenged the role of vitamin D supplementation in improving bone mineral density [58,59], supplementation of vitamin D has many beneficial effects [60,61,62,63]. However, many doctors and patients are concerned about whether vitamin D repletion will increase the risk of urolithiasis, especially in SFs [64]. A recent systematic review and meta-analysis demonstrated that long-term vitamin D supplementation resulted in increased risks of hypercalcemia and hypercalciuria, but did not increase risk of kidney stones [55].…”