Reproducibility over time of measurements of androgens, estrogens and hydroxy estrogens in urine samples from post-menopausal women

Abstract

Sex steroid concentrations in urine samples from post-menopausal women have been associated with risk of various chronic diseases. The basic requirement for the assessment of risk in such largescale epidemiological studies is that subjects be ranked accurately by their average, long-term hormone levels. We examined the reproducibility over time of measurements of urinary testosterone (T), 5a-androstane-3a, 17b-diol (ADIOL), estrone (E1), estradiol (E2), 2-hydroxy estrone and 2-hydroxy estradiol, (2(OH)-E), 16a-hydroxyestrone (16a(OH)-E1) and the ratio of 2(OH)-E and 16a(OH)-E1, in a representative sub-sample of post-menopausal women (n ¼ 43) participating in an ongoing prospective cohort study. Women collected three first morning urine voids on different occasions, with average time difference between the first and the third urine sample of 5.1 years. T, ADIOL, E1 and E2 were measured by radio immunoassay after enzymatic hydrolysis, solidphase extraction and HPLC purification of the samples, while 2(OH)-E and 16a(OH)-E1 were assayed by solid-phase enzyme immunoassay after enzymatic hydrolysis. Intra-class correlation co-efficients (ICCs) over time were very good for T (r ¼ 0.85), acceptable for E2, E1 and ADIOL (r > 0.55), but low for 2(OH)-E, 16a(OH)-E1 and their ratio (r < 0.46). The adjustment for creatinine concentrations did not increase these correlations.