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

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.