LAUSR

INTRODUCTION AND OBJECTIVE: Increasing age, male gender, and metabolic syndrome are associated with kidney stone formation. As sex hormones change with age, gender and metabolic syndrome, we hypothesized that sex hormones underlie the physiologic changes affecting stone formation because of the gender disparity seen with renal stones (males >> females). METHODS: Using the National Health and Nutrition Survey (NHANES) results from 2013-2016, we performed a cross-sectional nested case-control study using data on 3767 male participants and 3994 female participants. We performed a logistic regression analysis to analyze the predictive value of low testosterone on history of kidney stone, controlling for age and BMI in both males and females. For males, low testosterone was defined as Low (< 300 ng/dL) or Normal (> 300 ng/dL), in females Low Testosterone (< 10 ng/dL) or Normal (>10 ng/dL). Estrogen in males was defined as Low (<10 pg/ mL) or normal (> 10 pg/mL) and in females was categorically defined as Low (< 10 pg/mL) or Normal (> 10 pg/mL). Additionally, age (years), and BMI in (Kg/M̂2) were investigated. Self-reported history of kidney stone diagnosis was the outcome. RESULTS: Using logistic regression adjusting for age and BMI, low testosterone was independently associated with a history of kidney stones in males (OR[1.392, 95% CI: 1.101-1.759). There was no significant association between estrogen and stone formation in males. Neither estrogen nor testosterone were significantly associated with stone formation in Females. Strengths include this being the first study to report association between testosterone levels and renal stone prevalence in a contemporary cohort. Limitations of our study include the possible presence of confounding factors such as environmental influences and diabetes on serum testosterone as well as sampling bias due to incomplete response rates. CONCLUSIONS: Low testosterone is associated with kidney stones in men. Whether this association reflects a common causal pathway or shared risk factors such as metabolic syndrome requires additional investigation. Further studies matching menopausal status for women are necessary to investigate the relationship between estrogen and protection against kidney stones.