Thyroid Hormones in Fetal Central Nervous System Development

Abstract

Thyroid hormones are important for normal development of the human central nervous system (CNS). It is well established in children with congenital hypothyroidism that neonatal thyroid hormone deficiency significantly impairs subsequent neurodevelopment. In these children, the period of thyroid hormone insufficiency, which can begin in utero and extend until thyroid status is restored to normal in the neonatal period, determines the severity and type of defect manifested. While prompt and optimal thyroid hormone supplementation, following newborn screening is associated with far improved outcome and near normal development, subtle specific neurodevelopmental differences are still detectable compared to euthyroid controls. Because the particular impairments reflect the exact period of thyroid hormone insufficiency postnatally, as well as during gestation, this implies that brain development is not only thyroid hormone dependent in the neonatal period, but also prior to birth.

A mechanistic view of polybrominated diphenyl ether (PBDE) developmental neurotoxicity

“…Thyroid hormones are known to play a relevant role in brain development (Chan and Rovet, 2003; LaFranchi et al 2005), and hypothyroidism has been associated with a large number of neuroanatomical and behavioral effects (Haddow et al 1999; Zoeller and Crofton, 2005). Since the structurally similar polychlorinated biphenyls (PCBs) had been found to perturb thyroid hormone homeostasis, the possibility that PBDEs may act through similar mechanisms has been extensively investigated.…”

Developmental neurotoxicity of polybrominated diphenyl ether (PBDE) flame retardants

“…Thyroid hormones are known to play a relevant role in brain development (Chan and Rovet, 2003;LaFranchi et al 2005), and hypothyroidism has been associated with a large number of neuroanatomical and behavioral effects (Schalock et al 1977;Haddow et al 1999;Zoeller and Crofton, 2005). Several chemicals can disrupt thyroid function leading to a decrease in thyroxine (T 4 ).…”

Visual Abilities at 6 Months in Preterm Infants: Impact of Thyroid Hormone Deficiency and Neonatal Medical Morbidity

“…It is well established that TH is critical for normal brain development, including development of structures necessary for visual processing (13)(14)(15). During pregnancy, maternal TH crosses the placenta into the fetal circulation (16). Because of the delayed maturation of the fetal thyroid system, maternal TH is the fetus' sole source of hormone in early gestation (17), and over the course of gestation, this reliance on maternal TH supply diminishes to assume full thyroid function at term.…”