Hypercalciuria and urinary saturation measurements in climacteric women

Fifteen percent (20/130) of a group of climacteric women on diets of their choice had urinary calcium (Ca) levels exceeding 4 mg/kg per day. Most of these hypercalciuric subjects had a daily Ca intake of 0.4-0.5 g. Their bone turnover rates were raised and high Ca absorption was observed in 4 cases. Serum Ca and total protein and glomerular filtration rates were normal in all the hypercalciuric patients. The calcium/creatinine (Ca/Cr) ratio (mg l-1/mg l-1, fasting, 09:00-10:00 h) was measured in 72 climacteric women, 35 of whom (49%) had ratios > 0.1. The latter defines a relative hypercalciuria as compared with premenopausal Ca excretion levels. Only 5 of the 35 subjects had calciuria levels above 4 mg/kg per day. The Ca/Cr ratio cannot replace daily urinary Ca measurements for the screening of subjects in whom calciuria may exceed net Ca absorption. Urinary saturation measurements were carried out in 70 women. Supersaturation was observed only in the case of Ca oxalate (CaOx) among several calcium salts usually found in urinary stones. CaOx supersaturation was observed in 95% of the hypercalciuric subjects and in 48% of the rest of the women investigated. The relatively high frequency of CaOx supersaturation can be attributed in part to the decreased excretion of citrate associated with ovarian failure. Oestrogen replacement therapy increased citrate excretion and lowered the level of CaOx supersaturation. Ca supplementation (1 g Ca/day) reduced the degree of supersaturation as a result of the concurrent reduction in oxalate excretion.