The effect of neonatal thyroidectomy on myelination in the rat brain

Balázs, R.; Brooksbank, B. W. L.; Davison, Alan; Eayrs, J. T.; Wilson, David A.

doi:10.1016/0006-8993(69)90321-7

Cited by 194 publications

(56 citation statements)

References 27 publications

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“…Their absence during development leads to irreversible brain damage (1)(2)(3). The defects resulting from thyroid hormone deficiency in the developing brain are well described both for congenital hypothyroidism and endemic cretinism (4)(5)(6), but the biochemical mechanisms involved are not yet fully defined (7,8), nor the timing at which the developing brain is more sensitive to the absence of thyroid hormones. Nuclear receptors for T3 have been described in the adult and fetal brain (9)(10)(11)(12) but the postreceptor events are also still poorly understood.…”

mentioning

confidence: 99%

Developmental Changes in Rat Brain 5′-Deiodinase and Thyroid Hormones during the Fetal Period: The Effects of Fetal Hypothyroidism and Maternal Thyroid Hormones

Oña¹,

Obregón²,

Rey³

et al. 1988

Pediatr Res

109

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ABSTRACT. We have studied the ontogenesis of 5'-deiodinase (5'D) activity in rat brain during fetal life, its capacity to respond to maternal or fetal hypothyroidism, and its regulation by maternal thyroid hormones. Type I1 5'D (5' D-11) activity increases 4-fold during the period studied (17 to 22 days of gestation), mainly between days 19 and 21. Fetal brain T4 concentrations increase in parallel with fetal plasma T4, whereas fetal brain T3 concentrations increase 18 times (days 17-21), six times more than would have been expected from the small increase in fetal plasma T3 levels. Maternal thyroidectomy did not affect 5'D-I1 activity or thyroid hormone concentrations in fetal brain (except brain T4 at 18 days of gestation). Fetal hypothyroidism, induced by giving a goitrogen (methimazole) to the mothers, depleted all fetal tissues studied, including the fetal thyroid, from thyroid hormones. By 19 days of gestation, the fetal brain was able to respond to hypothyroidism with a 3-to 5-fold increase in 5'D-I1 activity. Earlier onset of treatment with methimazole led to 2-to 3-fold increases in 5'D already at 17 and 18 days of gestation, showing that when fetal thyroid secretion starts the fetal brain 5'D-I1 is able to respond to hypothyroidism. Replacement of methimazole-treated mothers with physiological doses of T4, given by constant infusion, increased T4 and T3 concentrations in fetal brain, and inhibited fetal, as well as maternal, brain 5'D-I1 activity. But treatment of the mothers with T3 did not change T3 concentrations in the fetal brain, despite the increase in fetal plasma T3, and actually increased 5'D-I1 in fetal brain. Maternal cerebral 5'D-I1 was not inhibited by T3 treatment. Inverse relationships were found between the 5'D-I1 and thyroid hormone concentrations in the fetal brain. These correlations were not identical for fetuses from thyroidectomized and control mothers. In fetuses from thyroidectomized dams, brain 5'D-I1 is more sensitive to a decrease in brain T4 than in the progeny of control

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confidence: 99%

Developmental Changes in Rat Brain 5′-Deiodinase and Thyroid Hormones during the Fetal Period: The Effects of Fetal Hypothyroidism and Maternal Thyroid Hormones

Oña¹,

Obregón²,

Rey³

et al. 1988

Pediatr Res

109

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“…Studies have indicated that hypothyroidism leads to delay in creation and weakening of myelin (Balazs, 1969). Thyroid hormones have an important role in differentiation of oligodendrocytes and cause defects in axonal maturation .…”

Section: Discussionmentioning

confidence: 99%

Evaluation of the BDNF, NGF, NT3 and NT4 Genes Expressions in the Brains of Neonatal Mice with Hypothyroidism

Bhroz¹,

Parivar²,

Amiri³

et al. 2017

JMBR

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Background and Aim: Thyroid is one of the endocrine glands, (T3 and T4) play a significant role in the development of prenatal brain and the following stages. The study aimed to evaluate the effect of hypothyroidism on the amount of expression of NT4, NT3, nerve growth factor (NGF) and brain-derived neurotrophic factor (BDNF) in brain of one-day rat neonates with hypothyroidism. Materials and Methods:In total, 25 mature mice of Albino NMRI race were selected after mating, divided into three group, control, as well as low-dose and high-dose intervention groups. Samples of the control group received pure water during pregnancy, whereas subjects of the intervention group with low and high doses of the medication were administered with 20 mg and 100 mg methimazole powder (dissolved in 100 cc water), respectively. After child delivery, blood samples were obtained from mother mice to determine the level of T3 and T4 in blood serum. Following that, the brain of one-day mice were removed by surgery and assessed to determine the amount of expression of NT4, NT3, NGF and BDNF using the complete kit of RT-PCR.Results: Levels of T4 and T3 in the control group were 28 ug/dl and 1.59 ug/dl, respectively. In the low-dose intervention group, the amounts of the mentioned hormones were 8 ug/dl and 0.85 ug/dl, significantly, indicating a significant reduction in the expression of NT4, NT3, NGF and BDNF genes, compared to the control group. Moreover, T4 and T3 were 6 ug/dl and 0.79 ug/dl in the high-dose group, respectively, conveying a significant decrease in the expression of NT4, NT3, NGF and BDNF genes, compared to the control group (P<0.05).

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“…Neuronal bodies are smaller and more densely packed, there is diminished dendritic branching and elongation, as well as altered distribution of dendritic spines and delayed cell proliferation and migration (Nicholson & Altman 1972). Deficiencies of myelination have been observed in the cerebral cortex, visual and auditory cortex, hippocampus and cerebellum, areas which relate to the observed neurodevelopmental delay (Balazs et al 1969, Rosman et al 1972. These findings, together with a marked decrease in the number and delayed maturation of microtubules within these cells, indicate potentially profound changes in the central nervous system compared with the euthyroid state (Legrand 1967, Faivre et al 1984.…”

Section: Central Nervous System Histology and The Effects Of Thyroid mentioning

confidence: 99%

Thyroid hormone and central nervous system development

Chan¹,

Kilby²

2000

Journal of Endocrinology

187

115

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The effect of neonatal thyroidectomy on myelination in the rat brain

Cited by 194 publications

References 27 publications

Developmental Changes in Rat Brain 5′-Deiodinase and Thyroid Hormones during the Fetal Period: The Effects of Fetal Hypothyroidism and Maternal Thyroid Hormones

Developmental Changes in Rat Brain 5′-Deiodinase and Thyroid Hormones during the Fetal Period: The Effects of Fetal Hypothyroidism and Maternal Thyroid Hormones

Evaluation of the BDNF, NGF, NT3 and NT4 Genes Expressions in the Brains of Neonatal Mice with Hypothyroidism

Thyroid hormone and central nervous system development

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