Effects of maternal exposure to chlorinated diphenyl ethers on thyroid hormone concentrations in maternal and juvenile rats.

Polychlorinated diphenyl ethers (PCDEs) are industrial byproducts and widespread environmental contaminants. Their structural similarity to PCBs suggests that they may exhibit subtle effects on both adult and juvenile mammals. We examined the effects of 3 PCDEs (2,2',4,5,6'-pentachlorodiphenyl ether, 2',3,4,6'-tetrachlorodiphenyl ether, and 2,2',4,4',5,5'-hexachlorodiphenyl ether) on maternal rat thyroid levels shortly after exposure, and on the thyroid levels of 16 day old juvenile rats that had been prenatally exposed. Both 2,2',4,5, 6'-pentachlorodiphenyl ether and 2',3,4,6'-tetrachlorodiphenyl ether depressed thyroxine (T4) levels in the maternal females as well as in both sexes of juvenile rats. 2,2',4,4',5,5'-hexachlorodiphenyl ether did not alter T4 levels in the pregnant females, but depressed juvenile T4 levels. None of the congeners studied significantly altered T3 levels. Effects on thyroid hormones did not correlate with the congeners' induction of cytochrome P450.