An article published in Environmental Health Perspectives (June 2000;108(Suppl 3):433–438) reviewed the essential role of the thyroid gland in brain development and examined how environmental chemicals may interfere with this process. Adequate thyroid hormone levels are especially critical during fetal development and the early months after birth, a period marked by rapid brain growth and the formation of neural connections.
Animal research reviewed in the article showed that exposure to environmental chemicals such as polychlorinated biphenyls (PCBs) and dioxins can impair both thyroid function and neurological development. These compounds have been shown to enlarge the thyroid gland and reduce circulating levels of thyroxine (T4). Some environmental chemicals can also mimic natural thyroid hormones and bind to the transport proteins that normally carry thyroid hormones throughout the body. By competing with natural hormones, these substances may disrupt normal hormonal signaling and interfere with brain development.
Because thyroid function is closely linked to nervous system development, reducing exposure to environmental toxins may be an important factor in supporting healthy brain development throughout life.
For a broader overview of thyroid symptoms, testing, and thyroid disorders, see Thyroid Health: Symptoms, Testing, and Common Thyroid Disorders.
For more on the importance of thyroid hormones during pregnancy and early brain development, see Thyroid Function During Pregnancy and Child Brain Development.
