Calcium nephrolithiasis is associated with an increased risk of osteoporosis and fracture. Hypercalciuria has been assumed to be pathogenic for bone loss in kidney stone formers (KSF), although this association was shown in small cross-sectional studies.
We explored the association of urine calcium (UCaV) with bone mineral density (BMD) in KSF.
We retrospectively studied BMD in KSF. Excluded were subjects with hypercalcemia, chronic bowel disease, primary hyperparathyroidism, distal renal tubular acidosis or endogenous creatinine clearance <40 ml/min. We included 250 males and 182 females, subdivided into premenopausal, estrogen-treated postmenopausal (E+) (N=145) and non-estrogen-treated postmenopausal (E-) (N=37). We assessed the association between lumbar spine (LS) and femoral neck (FN) BMD and 24-hour UCaV (under random and restricted diet, and fasting state) using univariable and multivariable models adjusting for BMI, urine sodium and sulfate.
In multivariable analysis, no significant association found between UCaV under random and restricted diet, or fasting conditions (FS), and FN or LS BMD in men and E+ women. In E- women, LS BMD was inversely correlated with UCaV with restricted diet (r=-0.38, P=0.04 and adjusted r=-0.45, P=0.02) and in FS (r=-0.42, P=0.05).
Unlike previous small cross-sectional studies, we found no significant relationship between UCaV and BMD in a large group of calcium KSF. However, a significant inverse relationship was found in E- KSF only. This study suggests that mechanism(s) other than hypercalciuria explain lower BMD and higher fracture risk in patients with KSF, and highlights the role of estrogen on integrity of the bone.
The Journal of urology. 2017 Jan 04 [Epub ahead of print]
Khashayar Sakhaee, Naim M Maalouf, John Poindexter, Beverley Adams-Huet, Orson W Moe
Department of Internal Medicine, Division of Mineral Metabolism; Charles and Jane Pak Center for Mineral Metabolism and Clinical Research. Electronic address: ., Department of Internal Medicine, Division of Mineral Metabolism; Charles and Jane Pak Center for Mineral Metabolism and Clinical Research., Charles and Jane Pak Center for Mineral Metabolism and Clinical Research., Charles and Jane Pak Center for Mineral Metabolism and Clinical Research; Department of Clinical Sciences., Charles and Jane Pak Center for Mineral Metabolism and Clinical Research; Department of Internal Medicine, Division of Nephrology; Department of Physiology, The University of Texas Southwestern Medical Center at Dallas, Dallas, TX.
Go Beyond the Abstract with a commentary written by the authors