Sex steroid hormone levels may not explain gender differences in development of nephrolithiasis

Objectives: To determine whether serum sex steroid hormone levels, or the subsequent change in those levels over time, represent a risk factor for the development of nephrolithiasis in men. Methods: We retrospectively identified patients participating in a long-term cohort study (Rochester Epidemiology Project) in Olmsted County, Minnesota. Patients had previously undergone baseline detailed clinical examination and sex steroid hormone studies, including estradiol, testosterone, and bioavailable testosterone. Patients were followed on a biennial basis. Records were then reviewed to assess for formation of nephrolithiasis. Results: We identified 684 patients, with a median follow-up for stone formation of 12.8 years. All 684 patients had measurement of testosterone, of which 78.9% were in normal range. Five hundred eighteen men had baseline-free testosterone, of whom 88.6% were normal. Three hundred seventy-one patients had baseline estradiol, of whom 88.7% were normal. One hundred two men (14.9%) were found to have stones, with 61 of those (59.8%) occurring before first hormone measurement and 41 (40.2%) occurring after. On multivariate analysis, there was no significant association of serum hormones with nephrolithiasis, although a trend toward higher baseline testosterone and stones was seen (odds ratio [OR] 1.29; 95% confidence intervals [CI] 0.71, 2.33). Using a time-to-event for incident stone formation, we found no significant association of baseline hormones or percentage change in hormone levels over time with risk of stones. Conclusion: We found no significant association of sex steroid hormone levels with the risk of nephrolithiasis formation in men, although a weak trend toward an increased risk with elevated testosterone was seen.