The menace of endocrine disruptors on thyroid hormone physiology and their impact on intrauterine development

Abstract

The delivery of the appropriate thyroid hormones quantity to target tissues in euthyroidism is the result of unopposed synthesis, transport, metabolism, and excretion of these hormones. Thyroid hormones homeostasis depends on the maintenance of the circulating 'free' thyroid hormone reserves and on the development of a dynamic balance between the 'free' hormones reserves and those of the 'bound' hormones with the transport proteins. Disturbance of this hormone system, which is in constant interaction with other hormone systems, leads to an adaptational counter-response targeting to re-establish a new homeostatic equilibrium. An excessive disturbance is likely to result, however, in hypo- or hyper- thyroid clinical states. Endocrine disruptors are chemical substances forming part of 'natural' contaminating agents found in most ecosystems. There is abundant evidence that several key components of the thyroid hormones homeostasis are susceptible to the action of endocrine disruptors. These chemicals include some chlorinated organic compounds, polycyclic aromatic hydrocarbons, herbicides, and pharmaceutical agents. Intrauterine exposure to endocrine disruptors that either mimic or antagonize thyroid hormones can produce permanent developmental disorders in the structure and functioning of the brain, leading to behavioral changes. Steroid receptors are important determinants of the consequences of endocrine disruptors. Their interaction with thyroid hormones complicates the effect of endocrine disruptors. The aim of this review is to present the effect of endocrine disruptors on thyroid hormones physiology and their potential impact on intrauterine development.

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“…2006;Rovet 2002;Zoeller and Rover 2004). This is also supported experimentally, where developmental hypothyroidism causes the deficits in passive avoidance, spatial learning, and operant conditioning (Brosvic et al 2002;Darbra et al 2003Darbra et al , 2004, stunted growth, impaired brain development, and mental retardation (Anderson et al 2003;Bernal et al 2003;Goodman and Gilbert 2007;Mastorako et al 2007;Zoeller and Rover 2004).…”

Environmental Hazards Education for Childbirth Educators

“…By the end of the second trimester, the fetus has the ability to ''mount antigen-specific responses'' to viruses and parasites (Hertz-Picciotto et al, 2008, p. 147). Prenatal exposures to environmental hazards have been shown to cause dysregulation of these processes (HertzPicciotto et al, 2008;Mastorakos, Karoutsou, Mizamtsidi, & Creatsas, 2007).…”

“…During fetal life, thyroid hormones contribute to the process of differentiation of tissues; when the availability of these hormones is decreased, irreversible developmental disorders of the fetus can occur (Mastorakos et al, 2007). The developmental programming hypothesis, which proposes that early development determines subsequent organ functions and disease risks, has gathered much support from both experimental and epidemiological studies.…”

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