The relationship between urinary sodium excretion and bone mineral metabolism of climacteric women in Korea / 대한내과학회지

ABSTRACT

BACKGROUND: High oral intake of sodium is known to increase urinary calcium excretion in hypercalciuria and renal-stone formers, and there is well-documented correlation between urinary sodium and calcium excretion in 24-hour urine collections from normal subjects and postmenopausal women. The present study was aimed to investigate relationship between urinary sodium excretion and bone mineral metabolism of climacteric women in Korea. METHODS: We measured 24-hour urinary sodium, calcium, and creatinine level; serum osteocalcin level, serum alkaline phosphatase (ALP) level, serum follicular stimulating hormone (FSH) level; urine deoxypyridinoline (DPD) level; and bone mineral density (BMD) in 430 climacteric women in Korea (331 postmenopausal and 99 premenopausal women). RESULTS: The postmenopausal women had higher (p<0.05) value for mean urinary sodium to creatinine ratio of 0.225+/-0.078 mmol/mg vs. 0.209+/-0.061 mmol/mg and higher (p<0.001) value for mean urinary calcium to creatinine ratio of 0.261+/-0.125 mg/mg vs. 0.209+/-0.081 mg/mg than the premenopausal women. Significant positive correlation was noted between urinary sodium to creatinine ratio and urinary calcium to creatinine ratio (r=0.426, p<0.001). Negative correlation was found between urinary sodium to creatinine ratio and femur neck BMD (r=-0.099, p<0.05). Although urinary sodium to creatinine ratio was not significantly correlated to serum FSH level (r=0.066, p=0.088), serum ALP level (r=0.067, p=0.083), urine DPD level (r=0.077, p=0.056), and lumbar BMD (r=-0.067, p=0.083), but there is a weak trend in it. CONCLUSION: There is not only an increase in urinary sodium excretion at postmenopausal women, but also an increase in the urinary calcium excretion. It seems that subjects with a high urinary sodium excretion show a higher urinary calcium excretion that may have some effect on bone mineral metabolism. However, further studies are required to establish whether urinary sodium excretion have a direct effect on bone mineral metabolism of climacteric women in Korea.