Journal Article

PTH and 1.25 vitamin D response to a low-calcium diet is associated with bone mineral density in renal stone formers

Andreas Pasch, Felix J. Frey, Ute Eisenberger, Markus G. Mohaupt and Olivier Bonny

in Nephrology Dialysis Transplantation

Published on behalf of European Renal Association - European Dialysis and Transplant Assoc

Volume 23, issue 8, pages 2563-2570
Published in print August 2008 | ISSN: 0931-0509
Published online April 2008 | e-ISSN: 1460-2385 | DOI: http://dx.doi.org/10.1093/ndt/gfn091
PTH and 1.25 vitamin D response to a low-calcium diet is associated with bone mineral density in renal stone formers

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Background. Renal calcium stones and hypercalciuria are associated with a reduced bone mineral density (BMD). Therefore, the effect of changes in calcium homeostasis is of interest for both stones and bones. We hypothesized that the response of calciuria, parathyroid hormone (PTH) and 1.25 vitamin D to changes in dietary calcium might be related to BMD.

Methods. A single-centre prospective interventional study of 94 hyper- and non-hypercalciuric calcium stone formers consecutively retrieved from our stone clinic. The patients were investigated on a free-choice diet, a low-calcium diet, while fasting and after an oral calcium load. Patient groups were defined according to lumbar BMD (z-score) obtained by dual X-ray absorptiometry (group 1: z-score <−0.5, n = 30; group 2: z-score −0.5–0.5, n = 36; group 3: z-score >0.5, n = 28). The effect of the dietary interventions on calciuria, 1.25 vitamin D and PTH in relation to BMD was measured.

Results. An inverse relationship between BMD and calciuria was observed on all four calcium intakes (P = 0.009). On a free-choice diet, 1.25 vitamin D and PTH levels were identical in the three patient groups. However, the relative responses of 1.25 vitamin D and PTH to the low-calcium diet were opposite in the three groups with the highest increase of 1.25 vitamin D in group 1 and the lowest in group 3, whereas PTH increase was most pronounced in group 3 and least in group 1.

Conclusion. Calcium stone formers with a low lumbar BMD exhibit a blunted response of PTH release and an apparently overshooting production of 1.25 vitamin D following a low-calcium diet.

Keywords: 1.25 vitamin D; bone mineral density; hypercalciuria; nephrolithiasis; parathyroid hormone

Journal Article.  5226 words.  Illustrated.

Subjects: Nephrology

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