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Epidemiology:
Program and Abstracts: The Seventeenth Conference of the International Society for Environmental Epidemiology (ISEE): Abstracts

SERUM DIOXIN CONCENTRATIONS AND RISK OF UTERINE FIBROIDS

Eskenazi, B*; Warner, M*; Samuels, S†; Young, J*; Jewell, N*; Gerthoux, P M.‡; Needham, L L.§; Patterson, D G. Jr§; Castorina, R*; Olive, D O.¶; Vercellini, P∥; Mocarelli, P‡

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*School of Public Health, University of California, Berkeley, CA, USA; †School of Public Health, State University of New York at Albany, Albany, NY, USA; ‡Department of Laboratory Medicine, University of Milano-Bicocca, School of Medicine, Hospital of Desio, Desio-Milano, Italy; §Division of Environmental Health Laboratory Science, National Center for Environmental Health, Centers for Disease Control and Prevention, Atlanta, GA, USA; ¶Department of Obstetrics and Gynaecology, University of Wisconsin Medical School, Madison, WI, USA; ∥Department of Obstetrics and Gynaecology, Mangiagalli Hospital, University of Milan, Milan, Italy.

ISEE-68

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Introduction:

2,3,7,8-Tetrachlorodibenzo-p-dioxin (TCDD) is a widespread environmental contaminant and known endocrine disruptor. Studies in rats suggest an anti-oestrogenic response of TCDD in the uterus. Uterine fibroids, benign tumours accounting for one-third of all hysterectomies, are associated with reproductive dysfunction. The etiology of fibroids is unknown, however increased oestrogen receptor levels and enhanced expression of several oestrogen-regulated genes have been observed in fibroids. On July 10, 1976, as a result of a chemical explosion, residents of Seveso, Italy, experienced the highest levels of TCDD exposure in a human population. Twenty years later (1996-1998), we initiated the Seveso Women’s Health Study (SWHS), a retrospective cohort study, to determine whether the women were at higher risk for reproductive disease.

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Aim:

We will examine the association between serum TCDD levels and occurrence of uterine fibroids in the SWHS cohort.

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Methods:

The SWHS cohort comprises 981 women who were 0 to 40 years in 1976, resided in the most contaminated areas, Zones A and B, at the time of the explosion, and had archived sera collected soon after the explosion. Individual serum TCDD exposure was measured by high-resolution/mass spectrometry. Using current status modelling techniques, we will examine the relation of serum TCDD and uterine fibroids in two ways: 1) limiting to incident cases diagnosed by the study trans-vaginal ultrasound, and 2) including cases based on self-report.

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Results:

Of 413 women who were still menstruating, ≥32 years (youngest age of cases), and had an intact uterus, 88 cases (21%) of fibroids were diagnosed by study trans-vaginal ultrasound. Cases were older, less educated, had higher body mass index, were less likely to have used oral contraceptives, and reported a longer time since last pregnancy than non-cases. Lipid-adjusted serum TCDD levels for cases (n=88, median=“44.8” ppt, range: 2.5-3,830) was lower than for non-cases (n=325, median = 46.3 ppt; range: 2.5-5,710). In multivariate analysis, a 10-fold increase in serum TCDD (log TCDD) was associated with a non-significant reduced odds of fibroids (odds ratio (OR) = 0.93; 95% confidence interval (CI): 0.58 – 1.50). When TCDD was categorized, compared to the lowest exposure group (≤20 ppt), the OR (95% CI) for the two dose groups, 20.1-100 ppt, and >100 ppt, were 0.49 (0.25-0.97) and 0.68 (0.31-1.49), respectively. We will present the results of the expanded analysis which will include the full SWHS cohort (n=981) and as cases, women who self-report disease.

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Discussion:

These preliminary data suggest that TCDD may have anti-oestrogenic effects on the uterus, in contrast to apparently oestrogenic effects previously found in breast of SWHS.

© 2005 Lippincott Williams & Wilkins, Inc.

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