Comparative study of the effects of experimentally induced hypothyroidism and hyperthyroidism in some brain regions in albino rats

Abstract

Thyroid hormones (THs) play a crucial role in the development and physiological functioning of different body organs especially the brain. Therefore, the objective of this study was to show the histopathological effects of the different thyroid states on some brain regions (cerebrum and cerebellum) and the skeletal features of their newborns during the postnatal development from the 1st to 3rd week. The female white albino rats were allocated into 3 groups as follows: the experimental hypothyroidism group is induced by 0.02% methimazole (MMI) (w/v) in drinking water, while the experimental hyperthyroidism group is performed by exogenous T4 [from 50 to 200microg/kg body weight intragastric administration beside adding 0.002% T4 (w/v) to the drinking water] from the gestation day 1 to lactation day 21 and control group which received tap water. As well, both maternal hypo- and hyperthyroidism caused some malformation and developmental defects in the cerebellar and cerebral cortex of their newborns along the duration of the experiment. These degenerative symptoms became more prominent and widely spread at the 3rd postnatal week. Concomitantly, there were some degeneration, deformation and severe growth retardation in neurons of these regions in both treated groups throughout the experimental period. Moreover, the skeletal features of these newborns were accelerated in hyperthyroid group while these maturations were delayed partially in hypothyroid ones during the examined periods. These alterations, on both treated groups, were age and dose dependent. Thus, further studies need to be done to emphasize this concept.

Depressive Disorders and Thyroid Function

“…Concomitantly, there is some degeneration, deformation and severe growth retardation in neurons of these regions in both groups (El-Bakry et al, 2010). Therefore, TH play an important role in brain development, neuronal migration and axonal projection to target cells.…”

Dysfunction of Maternal Thyroid Hormones and Psychiatric Symptoms

“…The steady in the functions of gestational thyroid hormones (THs) displays major actions in the developing brain in particular the development and differentiation of neurons, oligodendrocytes, astrocytes and microglial cells (El-bakry et al, 2010;Ahmed, 2011Ahmed, , 2012aAhmed, ,b, 2013Ahmed, , 2014Ahmed, , 2015aAhmed, -c, 2016aAhmed, -d, 2017aAhmed, -u & 2018aAhmed et al, , 2013aAhmed et al, ,b, 2014Ahmed et al, , 2015aAhmed and Incerpi, 2013;Van Hercket al, 2013;ElGareib, 2014, Incerpi et al, 2014;Candelotti et al, 2015;De Vito et al, 2015;El-Ghareeb et al, 2016;Ahmed and El-Gareib, 2017;Moog et al, 2017).…”

Gestational Prooxidant-Antioxidant Imbalance may be at Higher Risk for Postpartum Thyroid Disease

“…Any reduction in the availability of THs might possibly disturb the fetal and neonatal development [1][2][3][4][5][6][7][8][9][10][24][25][26]. These imbalances resulting from the production of free radicals, lipid peroxidation (LPO), carbonylation and nitration, and reduce the enzymatic and non-enzymatic antioxidant defense system [2,5,6,[33][34][35].…”