Association of estrogen measurements in serum and urine of premenopausal women

Abstract

Aims: We evaluated conjugated and unconjugated urinary estrogen metabolites as surrogate biomarkers for serum levels of unconjugated E1 and E2 in premenopausal women. Materials & methods: Repeated blood and urine samples were analyzed for estrogens and their metabolites using radioimmunoassays and liquid chromatography/mass spectrometry. Results: The strongest correlation (r = 0.39) was observed between serum E1 and urinary E1 and E2. The correlations of urinary E2 (r = 0.35), E1 (r = 0.29), all E2 metabolites (r = 0.30), all E1 metabolites (r = 0.23) and total estrogens (r = 0.26) with serum E2 were only moderate although statistically significant. All correlations were substantially stronger for Whites than Asians. Conclusion: Urinary E2 emerged as the best predictor for serum E1 and E2, but the large intra-subject variability in urinary estrogen levels limits its use as a biomarker.