Autism Four Times Likelier When Mother's Thyroid Is Weakened

http://www.sciencedaily.com/releases/2013/08/130813111730.htm

Aug. 13, 2013 — Pregnant women who don't make nearly enough thyroid hormone are nearly 4 times likelier to produce autistic children than healthy women, report scientists from the Houston Methodist Neurological Institute and Erasmus Medical Centre in an upcoming Annals of Neurology.

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"It is increasingly apparent to us that autism is caused by environmental factors in most cases, not by genetics," said lead author Gustavo Román, M.D., a neurologist and neuroepidemiologist who directs the Nantz National Alzheimer Center. "That gives me hope that prevention is possible."

The researchers also found that autistic children had more pronounced symptoms if their mothers were severely deficient for T4, also called thyroxine. Mild T4 deficiencies in mothers produced an insignificant increase in autistic children's symptoms.
The most common cause of thyroid hormone deficiency is a lack of dietary iodine -- because both the thyroid hormones, T3 and T4, contain that element.

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It is well established that expecting mothers' poor thyroid function (whether caused by poor diet, disease, or genetics) can lead to serious problems with fetal brain development, but only in the last 10 years or so has hypothyroidism been implicated as a possible cause of autism spectrum disorders.

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