Maervoet Johan, Vermeir Griet, Covaci Adrian, Van Larebeke Nicolas, Koppen Gudrun, Schoeters Greet, Nelen Vera, Baeyens Willy, Schepens Paul, Viaene Maria K
Toxicological Centre, University of Antwerp, Wilrijk, Belgium.
Environ Health Perspect. 2007 Dec;115(12):1780-6. doi: 10.1289/ehp.10486.
Thyroid hormones are important regulators of brain 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.
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.
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.
A statistically significant inverse relationship between concentrations of organochlorine compounds and levels of both free triiodothyronine (fT3) and free thyroxine (fT4), but not thyroid-stimulating hormone, was observed. We found no association between concentrations of heavy metals and thyroid hormone levels.
Our results suggest that environmental chemicals may affect the thyroid system of human neonates. Although the differences in fT3 and fT4 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.
甲状腺激素是大脑发育的重要调节因子。在发育的关键时期，即使甲状腺激素供应出现短暂紊乱也可能导致严重的神经损伤。动物实验表明，某些环境污染物，包括重金属以及多氯联苯（PCBs）和二噁英等有机氯化合物，可干扰甲状腺激素稳态。然而，这些污染物是否会影响人类甲状腺激素的循环水平尚不清楚，因为现有研究结果并不一致。
本研究旨在探讨环境污染物浓度与人类脐血中甲状腺激素水平之间的可能关系。
我们测量了198名新生儿脐血中环境污染物[包括选定的多氯联苯、类二噁英化合物、六氯苯、p,p'-滴滴伊（二氯二苯二氯乙烯）、镉、铅]和甲状腺激素的浓度。
观察到有机氯化合物浓度与游离三碘甲状腺原氨酸（fT3）和游离甲状腺素（fT4）水平之间存在统计学上显著的负相关，但与促甲状腺激素无关。我们发现重金属浓度与甲状腺激素水平之间无关联。
我们的结果表明，环境化学物质可能会影响人类新生儿的甲状腺系统。尽管与有机氯化合物相关的fT3和fT4水平差异在正常范围内，但鉴于甲状腺激素在大脑发育中的重要性，观察到的干扰仍可能对个体儿童的神经发育产生不利影响。
