What are the sexual predilections of hypercalciuria?

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

The reference range of urinary calcium excretion for men generally is 275 mg or less per day, whereas in women the usual daily limit is only 250 mg. These reference values were created using large numbers of people (not calcium kidney-stone formers) to establish a reference range. The most likely reason for the discrepancy is that men are generally larger physically than women and have a correspondingly larger amount of material, such as calcium and uric acid, to excrete.

Clearly, stone development occurs when the chemical conditions are favorable, regardless of what any arbitrary reference range might be. For most practical purposes, the 250-mg/day limit for 24-hour urinary calcium excretion or a concentration of no more than 200 mg of calcium/liter of urine is used regardless of sex when the relative severity of hypercalciuria and overall risk of calcium kidney stone production are considered (see Table 1).

Postmenopausal women are more likely than men to demonstrate hypercalciuria. Hyperparathyroidism, which produces hypercalciuria, is more common in older women, and, because of concerns about their risk for osteoporosis, calcium supplementation is more popular with women.

In a study, women who developed calcium kidney stones had an average calcium intake that was 250 mg/day less than that of non–stone-forming women. This finding agrees with other studies that suggest that calcium stone formers should not restrict their calcium intake too aggressively.

When urinary chemistry and stone formation rate data were analyzed with the demographic information from a large national database of kidney stone formers, investigators found that obesity is a risk factor for kidney stone disease in women but not in men.

This finding is similar to that found in 2 large studies involving 81,000 women in the Nurses' Health Study and 51,000 men in the Health Professionals Follow-up Study. Investigators at Harvard who conducted these studies found that body size was a positive risk factor for kidney stone disease in women, but the correlation was much less significant in men. [7] The reason for this finding is unclear, but it may be related to estrogen levels. Whether this increased risk in women disappears when the excess body weight is lost is also unclear.

High-dose vitamin B-6 appears to be beneficial in women with calcium oxalate stone disease but probably not in men. Using data from more than 85,000 women with no history of kidney stones whose cases were monitored for 14 years, investigators found that those who took large amounts of vitamin B-6 had a significantly lower incidence of new calcium oxalate stone formation. A similar benefit of reduced calcium stone production from increased vitamin B-6 intake was not evident in an equivalent male study group. Similarly, carbohydrate intake was found to be a kidney stone dietary risk factor for women but not for men. (Incidentally, these studies found no benefit to dietary vitamin-C modifications in either men or women.)

As previously mentioned, pregnancy has long been thought to increase the incidence of urinary stones and hypercalciuria. Healthy, non–stone-producing pregnant women have been found to have hypercalciuria during all 3 trimesters.


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