Journal
ENVIRONMENTAL HEALTH PERSPECTIVES
Volume 115, Issue 12, Pages 1780-1786Publisher
US DEPT HEALTH HUMAN SCIENCES PUBLIC HEALTH SCIENCE
DOI: 10.1289/ehp.10486
Keywords
brain; cord blood; development; endocrine disruption; heavy metals; neonates; organohalogens; PCBs; thyroid
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BACKGROUND: Thyroid hormones are important regulators of bra-in development. During critical periods of development, even transient disorders in thyroid hormone availability may lead to profound neurologic impairment. Animal experiments have shown that certain environmental pollutants, including heavy metals and organochlorine compounds such as polychlorinated biphenyls (PCBs) and dioxins, can interfere with thyroid hormone homeostasis. Whether these contaminants can affect circulating levels of thyroid hormones in humans is unclear, however, because the results of available studies are inconsistent. OBJECTIVES: The aim of the present study is to examine the possible relationships between concentrations of environmental pollutants and thyroid hormone levels in human umbilical cord blood. METHODS: We measured concentrations of environmental pollutants [including selected PCBs dioxin-like compounds, hexachlorobenzene,,p,p'-DDE (dichlorodiphenyldichloroethylene), cadmium, lead] and thyroid hormones in the cord blood of 198 neonates. RESULTS: A statistically significant inverse relationship between concentrations of organochlorine compounds and levels of both free triiodothyronine (fT(3)) and free thyroxine (fT(4)) but not thyroid-stimulating hormone, was observed. We found no association between concentrations of heavy metals and thyroid hormone levels. CONCLUSIONS: Our results suggest that environmental chemicals may affect the thyroid system of human neonates. Although the differences in fT(3) and fT(4) levels associated with the organochlorine compounds were within the normal range, the observed interferences may still have detrimental effects on the neurologic development of the individual children, given the importance of thyroid hormones in brain development.
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