MP43-11 PROTECTIVE EFFECT OF POSTMENOPAUSAL HORMONE REPLACEMENT AGAINST UROLITHIASIS

Abstract

INTRODUCTION AND OBJECTIVE: Menopause is reported to be associated with increased urinary calcium excretion, which may enhance the risk for the development of urolithiasis. However, it remains controversial about whether postmenopausal hormone replacement is a risk factor for formation of urolithiasis. Therefore, we conducted a population-based retrospective cohort study to evaluate the effect of hormone replacement therapy (HRT) on the formation of urolithiasis. METHODS: We used data sourced from Longitudinal Health Insurance Database, which consists of one million randomly selected subjects from the National Health Insurance Research Database of Taiwan. Health Insurance System of Taiwan covers approximately 23 million people (98% of population). Women who were prescribed HRT continually for longer than 3 months during 1997 to 2009 were classified as HRT users; the others were classified as non-users. A total of 13724 HRT users aged ≥ 45 years in 1997 without previous diagnosis of urolithiasis were enrolled. A cohort of 13724 age and metabolic syndrome matched non-HRT users were enrolled as the control group. HRT users were followed from the date of commencing HRT until six months after discontinuation of HRT. Non-users were followed from 1 January 1997 to 31 December 2009. Stratified cox regression model was used to examine the risk of subsequent urolithiasis between HRT users and non-users. RESULTS: Of the sampled patients, HRT users had a significantly lower cumulative incidence of urolithiasis than non-users (4.66% vs 5.94%, p < 0.001). The log-rank test revealed that HRT users had significantly higher urolithiasis-free survival rates than non-users (p < 0.001). HRT users were found to be at 0.78 times the risk of urolithiasis than non-users (95% confidence interval 0.70–0.87, p < 0.001). We further divided the HRT users into two groups according to HRT regimens: estrogen-only vs estrogen combined with progestin. The hazard ratio for urolithiasis in the estrogen-only HRT users compared with non-users was 0.78 (95% confidence interval 0.61–0.99, p = 0.04) and 0.78 (95% confidence interval 0.70–0.88, p < 0.001) in the patients with combined regimen. CONCLUSIONS: HRT use was associated with a lower risk of urolithiasis independent of the regimen difference. Source of Funding: None