The appropriate maternal thyroxine (T4) and 3,5,3-triiodothyronine (T3) levels during the whole pregnancy are important for the normal fetal development(El-bakry et al., 2010; Ahmed, 2011, 2012a,b, 2013, 2014, 2015a-c, 2016a-d, 2017a-v, 2018a-s; Ahmed and Ahmed, 2012; Ahmed et al., 2008; 2010; 2012; 2013a,b, 2014, 2015a,b, 2018a,b; Ahmed and Incerpi, 2013;Van Herck et al., 2013; Ahmed and El-Gareib, 2014,Incerpi et al., 2014; Candelotti et al., 2015; De Vito et al., 2015; El-Ghareeb et al., 2016; Ahmed and El-Gareib, 2017).In particular, the level of T4 elevates by approximately 50% during the first trimester of gestation due to estrogen (E2) augmented the concentration of thyroxine binding globulin (TBG) and increased the peripheral T4 metabolism (Morreale de Escobar et al., 2000; Small ridge et al., 2004; Ahmed et al., 2008; Zimmermann, 2016; Tuccilli et al., 2017). The levels of maternal thyroid hormones (THs) depend on the concentration of iodine (Beaufrere et al., 2000; Pearce, 2014; Jin et al., 2017). The level of iodine sharply increases by 50% during the gestation (Zimmermann, 2016) to increase the production of THs and to cover the fetus needs and the elevation in the iodine excretion (Yarrington and Pearce, 2011). During this stage, fetuses get a fraction of maternal THs and iodine ingredient by the placenta and amniotic fluid.