Abstract : The study was investigated the effect of the high concentrations o 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 highest value in FOX1, NK2.1 and PAX8 concentration was in 1.8 gm followed by in concentration 0.06 gm , while the lowest value recorded in control group 224.49a±7.61 with significant differences at(p≤0.05) between the studied groups in both mother and embryo however, Conclusion :Depending on the obtained results , the current study was found the thyroid transcription factors were involved directly with excess iodine taken.