Estrogen replacement increased the citrate and calcium excretion rates in postmenopausal women with recurrent urolithiasis

Purpose: Epidemiological data indicate a sharp increase in urinary calcium stone formation after menopause. We investigated the role of menopausal estrogen replacement therapy on the urinary constituents and characteristics that may influence recurrent calcium oxalate stone disease. Materials and Methods: Urinary constituents in 28 postmenopausal women on estrogen replacement therapy for more than 6 months were compared with those in 41 women who had never been exposed to estrogen after menopause. These 2 groups had a history of recurrent calcium oxalate urolithiasis. A group of age matched, nonstone forming volunteers who were and were not on estrogen served as controls. Results: The 24-hour urine collection revealed significantly higher mean calcium plus or minus standard deviation (188.8 +/- 101.5 versus 129.2 +/- 80.9 mg./24 hours, p <0.01), citrate (576.6 +/- 237.9 versus 306.2 +/- 209.9 mg./24 hours, p <0.001) and agglomeration inhibition (203 +/- 106 versus 159 +/- 81 minutes, p <0.05) in stone forming women who were versus were not on estrogen. Conclusions: Higher urinary citrate and higher agglomeration inhibition in women exposed to estrogen may decrease the risk of subsequent calcium stone formation.