Abstract : The study was investigated the effect of high concentration exogenous iodine on the thyroid transcription factors. Methods : The study was included 3 groups as following Group (1): Involved 20 adult female rats, animals in this group administered distilled water and served as control.Group (2): Involved 15 adult female rats, animals in this group treated group animals in low dose of iodine (0.06 mg) ,Group (3): Involved 15 adult female rats, animals in this group treated group animals in medium dose of iodine( 0.18 mg), after 18 days of pregnancy the animals was sacrificed and the serum was collected to determination Rat Paired box protein (PAX-8), Rat Forkhead box protein E1(FOXE1), Rat Homeobox protein (Nkx-2.1) done by ELISA assay for the mother while the thyroid factors for embryo was determined after tissues disruption with glass Homogenizers for the thyroid gland, the results reported the mother brain parameters showed the highest ACh concentration was in 1.8 gm 86.18c±1.02 followed by in 0.06 gm ,the concentration was 66.5±1.03, while the lowest value recorded in control group however the highest BDNF concentration was in 1.8 gm 5.77b±1.33followed by in 0.06 gm was 3.86a±0.15, and the lowest value recorded in control group with significant at(p≤0.05) between studied groups. same findings in embryonic brain parameters which highest ACh concentration was in 1.8 gm 65.38c±1.02 followed by in 0.06 gm ,the concentration was 50.5b±1.03 , however the highest BDNF concentration was in 1.8 gm 3.67b±0.0883 followed by in 0.06 gm was 1.96a±0.0581, and the lowest value recorded in control group in both groups with significant at(p≤0.05) between studied groups. Conclusion, the current study was found the parameters were involved directly with excess iodine taken , which all the parameter were evaluated with iodine doses in both pregnant mother and embryos rats.