How does bone-density loss effect the prognosis of hypercalciuria?

Updated: Apr 23, 2019
  • Author: Stephen W Leslie, MD, FACS; Chief Editor: Vecihi Batuman, MD, FASN  more...
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Answer

Hypercalciuric stone formers have been demonstrated to have a lower average bone mineral density than non–stone formers matched for age and sex. Moreover, compared with normocalciuric stone formers, hypercalciuric patients have an average bone density that is 5-15% lower. [1] (In children with idiopathic hypercalciuria, bone mineral ̶ density measurements have consistently demonstrated Z-score reductions at the lumbar spine and, to a lesser extent, the femoral neck. [29] )

Bone loss is worsened if patients are placed on a calcium-restricted diet, as 99% of the body's calcium is stored in the bones. Fortunately, significant clinical bone loss is relatively rare. However, female hypercalciuric stone formers who become menopausal are at significantly greater risk of osteoporosis than their healthy female counterparts. The higher the urinary calcium excretion is, the greater the risk.

Untreated patients with an obligatory urinary calcium loss relatively unaffected by diet, as in renal leak hypercalciuria, renal phosphate leak, and resorptive hypercalciuria, develop a negative calcium balance that can result in osteopenia or osteoporosis.

Some patients may have a primary altered bone metabolism, as occurs in postmenopausal women with an estrogen deficiency. Thirty percent of hypercalciuric children already show evidence of bone loss, which suggests a metabolic disorder is responsible. Strong evidence exists suggesting that the underlying disorder causing the hypercalciuria is responsible for the bone demineralization, but other factors, such as an overly zealous dietary calcium restriction, undoubtedly play a role.


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