Comparison of metabolic changes for stone risks in 24-hour urine between non- and postmenopausal women

BACKGROUND: To explore the differences of 24-hour urine compositions associated with urolithiasis between non- and postmenopausal females. METHODS: The 24-hour urine samples of female participants were collected from May 2013 to July 2014 along with national cross-sectional study of urolithiasis among adults aged ≥18 years in China. The exclusion criteria for the participants were: serum creatinine > 133μmol/L, with urinary tract infection, gout, hyperthyroidism, malignancy, had a history of cancer, kidney stones, enterectomy, had taken thiazide diuretics, allopurinol, vitamin supplement, potassium citrate or calcium supplements during the past two weeks. The compositions associated with urinary stone in 24-hour urine were measured and compared between non-and postmenopausal women. RESULTS: A total of 603 24-hour urine samples of female participants were analyzed. 354 women with a mean age of 52.5± 14.03 (range 19–84) years met the criteria, including 160 non-menopausal women and 194 postmenopausal women. Compared to the non-menopausal women, postmenopausal women had a lower secretion of citrate (p = 0.043), magnesium (p = 0.001) and creatinine (p = 0.001) in 24h urine. Multivariate linear regression analysis showed that the menopause status was associated with the changes in magnesium (p = 0.003) and creatinine (p = 0.002) secretion, whereas not with the changes in citrate (p = 0.402) secretion. CONCLUSIONS: Postmenopausal women have a significant lower secretion of magnesium in their 24-hour urine than non-menopausal ones. We suppose that might be associated with increased risk of urinary stone formation among postmenopausal women.