Thyroid hormones (THs) regulate the brain development(El-bakry et al., 2010; Ahmed, 2011,2012a,b, 2013, 2014, 2015a-c, 2016a-d, 2017a-f; Ahmed et al., 2008, 2010, 2012, 2013a,b, 2014; 2015a,b; Ahmed and Ahmed,2012; Ahmed and Incerpi, 2013;Van Hercket al., 2013; Ahmed andElGareib,2014;Incerpi et al., 2014; Candelotti et al., 2015; De Vito et al., 2015; El-Ghareeb et al., 2016; Ahmed and El-Gareib, 2017). The cholinergic system [acetylcholinesterase (AchE) and butyrylcholinesterase (BuchE)] (Carageorgiou et al., 2007; Tousson et al., 2012), and the neuronal development (Hadj-Sahraoui et al., 2000; Zhang et al., 2009) might disturb by neonatal thyroid deficiency (Ahmed andEl-Gareib, 2014; Ahmed et al., 2014).Also, these might diminish the development of cholinergic synapses and brain function. In contrast, hyperthyroidism can accelerate the development of the cholinergic neurons (Gould and Butcher, 1989; Ahmed et al., 2008). Thus, any thyroid disorders might be associated with neuro developmental defects through decreasing T3 level (Sawin et al., 1998) by recruitment of its transcriptional corepressors and/or dissociation of coactivators (Moriyama et al., 2007).