Effects of long-term excessive Iodine intake on the maternal-fetal thyroid hormone metabolism in mice

Long-term excessive iodine intake resulted in an increased TT_4 level and a decreased TT_3 level in maternal serum,meanwhile,hepatic and renal type 1 deiodinase activity decreased dose-dependently.A significant reduction in type 2 deiodinase ( D2 ) activity of 12.5 d placenta was found in 3.0 mg/L or above groups.For 19.5 d uterus,D2 activity decreased and type 3 deiodinase activity increased.The results suggest that excessive iodine has an effect on the embryonic development by regulating maternal-fetal thyroid hormone metabolism.