Endocrine disruption in human placenta: expression of the dioxin-inducible enzyme, CYP1A1, is correlated with that of thyroid hormone-regulated genes.

Context: Thyroid hormone (TH) is essential for normal development; therefore, disruption of TH action by a number of industrial chemicals is critical to identify. Several chemicals including polychlorinated biphenyls are metabolized by the dioxin-inducible enzyme CYP1A1; some of their metabolites can interact with the TH receptor. In animals, this mechanism is reflected by a strong correlation between the expression of CYP1A1 mRNA and TH-regulated mRNAs.