Vitamin D repletion does not alter urinary calcium excretion in healthy postmenopausal women.
OBJECTIVE
To evaluate, in a posthoc analysis of a previous study, whether vitamin D repletion in postmenopausal women with insufficient vitamin D increases urinary calcium excretion, as vitamin D therapy might contribute to hypercalciuria and calcium stones in susceptible individuals, and the effect of vitamin D on the risk of urolithiasis warrants attention.


METHODS
We recruited 18 women at > or =5 years after menopause who had vitamin D insufficiency (serum 25(OH)-vitamin D, 16-24 mg/dL). We excluded women with a history of urolithiasis and kidney disease. Women had one calcium absorption study when vitamin D-insufficient, received vitamin D therapy, and completed a second calcium absorption study when vitamin D-replete. We fed subjects meals that mirrored the nutrient composition from self-reported 7-day diet diaries. To measure calcium absorption, we collected urine for 24 h during both visits.


RESULTS
We achieved vitamin D repletion in all women (25(OH)-vitamin D before and after treatment, 22 and 63 mg/dL, respectively; P < 0.001). The mean calcium intake was 832 mg/day. Residual urine specimens were available for 16 women, allowing a measurement of 24-h urinary calcium. Calcium excretion did not change after vitamin D therapy (212 before vs 195 mg/day after; P = 0.60). Of four women with hypercalciuria (>247 mg/day), calcium excretion decreased in three (377-312 mg/day, not significant).


CONCLUSIONS
Vitamin D supplementation did not increase the urinary calcium excretion in healthy postmenopausal women. Many stone formers are at risk of premature bone loss, vitamin D insufficiency, or both. Based on the present results we suggest a study of patients with hypercalciuria and nephrolithiasis to determine the risks of vitamin D therapy.
Penniston
Kristina L
KL
Departments of Urology and Medicine, Osteoporosis Clinical Center and Research Program, University of Wisconsin School of Medicine and Public Health, Madison, WI, USA.
Jones
Andrea N
AN
Nakada
Stephen Y
SY
Hansen
Karen E
KE
D000368:Aged; D002118:Calcium / Q000652:urine*; D019587:Dietary Supplements; D005260:Female; D006801:Humans; D053565:Hypercalciuria / Q000139:chemically induced; D008875:Middle Aged; D010024:Osteoporosis / Q000517:prevention & control*; D017698:Postmenopause; D012307:Risk Factors; D052878:Urolithiasis / Q000139:chemically induced; D014807:Vitamin D / Q000008:administration & dosage / Q000009:adverse effects*; D014808:Vitamin D Deficiency / Q000150:complications / Q000188:drug therapy*; D014815:Vitamins / Q000008:administration & dosage / Q000009:adverse effects*
D014815:Vitamins; D014807:Vitamin D; D002118:Calcium