Thyroid Hormone System and Development

Abstract

In recent years, many studies have been published regarding thyroid hormones (THs)-disrupting effects of environmental chemicals. THs play a crucial role in normal fetal growth and maturation. Even before the fetal thyroid gland matures and starts to secrete THs, THs are detected in the fetal cerebral cortex, thereby confirming that fetuses completely rely on the maternal TH supply by the end of the first trimester. Therefore, exposure of pregnant women and their fetus to environmental chemicals that can interfere with THs has been of special concern. This chapter covers mainly recent findings on the epidemiological studies which investigated the associations between prenatal exposure to environmental chemicals and neonatal TH concentrations. In addition, possible mechanisms of thyroid-disrupting action by each chemical are drawn such as competitive bindings to TH transport proteins, interference of TH regulation, synthesis, and metabolism. Further, we emphasize a need for longitudinal studies to more completely assess whether the effects of chemical exposure on TH level, particularly during sensitive developmental windows, such as in fetal life and early infancy, are permanent. PU - SPRINGER-VERLAG SINGAPORE PTE LTD PI - SINGAPORE PA - 152 BEACH ROAD, #21-01/04 GATEWAY EAST, SINGAPORE, 189721, SINGAPORE