National Food Administration, PO Box 622, 751 26 Uppsala, Sweden.
Environ Int. 2010 Feb;36(2):180-7. doi: 10.1016/j.envint.2009.11.001. Epub 2009 Dec 1.
In experimental studies, it has frequently been observed that the homeostasis of thyroid hormones (THs) is affected by exposure to persistent organic pollutants (POPs), such as dioxins and PCBs. In man, similar effects have been indicated in several epidemiological studies. In order to investigate the possible effect on THs at low background exposures found among the Swedish population the following study was performed. Primiparous women (n=395) in the Uppsala region were recruited between 1996 and 1999. Of these, 325 mothers agreed to donate a serum sample in late pregnancy and breast milk was obtained from 211 women 3 weeks after delivery. Babies were sampled for blood at 3 weeks (n=150) and 3 months (n=115) after birth. In connection to the sampling, questions on personal characteristics were asked. Levels of low (tri- to penta-) chlorinated PCB, di-ortho PCB, p,p'-DDE, (mono-ortho) PCB TEQ and PCDD/DF TEQ were monitored in breast milk and in mother's blood (not PCDD/DF). The results showed that the measured TH levels (thyroid-stimulating hormone - TSH, total tri-iodothyronine - TT3, free thyroxine - FT4) in mothers and children were within the reference range. Some significant associations were seen between POP exposures and TH levels in mother or child after simple regression analysis. Following adjustment for important confounding factors, the significant associations mostly disappeared. However, significantly decreasing TT3 levels with increasing prenatal low-chlorinated PCB exposure were still seen in 3 week old children, and on TT3 in mothers exposed to PCDD/DF. In conclusion, the study clearly shows the importance of adjustment for important confounding factors in the analysis of possible associations between POP exposure and hormonal effects. The remaining associations are weak in both children and mothers and the clinical consequences of these alterations are uncertain. When comparing studies that investigate associations between TH levels and POP levels during the perinatal stage, no obvious between-study concordance was seen regarding the critical dose for hormonal effects to occur.
在实验研究中，经常观察到甲状腺激素（THs）的内稳态会受到持久性有机污染物（POPs）的暴露的影响，如二恶英和多氯联苯。在人类中，几项流行病学研究也表明了类似的影响。为了研究瑞典人群中低背景暴露对 THs 的可能影响，进行了以下研究。乌普萨拉地区的初产妇（n=395）于 1996 年至 1999 年期间招募。其中，325 位母亲同意在妊娠晚期捐献一份血清样本，211 位母亲在分娩后 3 周获得了母乳。婴儿在出生后 3 周（n=150）和 3 个月（n=115）时采血。在采样的同时，还询问了个人特征方面的问题。监测了母乳和母亲血液中低（三至五氯）代氯联苯、二-邻位 PCB、p,p'-DDE、（单-邻位）PCB TEQ 和 PCDD/DF TEQ 的水平（未监测 PCDD/DF）。结果表明，母亲和儿童的测量 TH 水平（促甲状腺激素 - TSH、总三碘甲状腺原氨酸 - TT3、游离甲状腺素 - FT4）在参考范围内。简单回归分析后，观察到 POP 暴露与母亲或儿童 TH 水平之间存在一些显著相关性。在调整了重要的混杂因素后，这些显著相关性大多消失。然而，在 3 周龄儿童中仍观察到随着产前低氯代 PCB 暴露的增加 TT3 水平逐渐降低，而在暴露于 PCDD/DF 的母亲中 TT3 水平也降低。总之，该研究清楚地表明，在分析 POP 暴露与激素效应之间的可能关联时，调整重要混杂因素非常重要。在儿童和母亲中，剩余的相关性较弱，这些变化的临床后果尚不确定。在比较研究围产期 TH 水平与 POP 水平之间的关联时，对于发生激素效应的临界剂量，没有明显的研究间一致性。
