GutFeeling
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Pregnant women who don't make nearly enough thyroid hormone are nearly 4 times likelier to produce autistic children than healthy women.
The association emerged from a study of more than 4,000 Dutch mothers and their children, and it supports a growing view that autism spectrum disorders can be caused by a lack of maternal thyroid hormone, which past studies have shown is crucial to the migration of fetal brain cells during embryo development.
"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.
Iodine deficiency is common throughout the world, including developed countries. The World Health Organization estimates nearly 1 in 3 people are affected globally. A 2005 CDC-University of Kansas study estimated that in the U.S., where iodine deficiency had been practically eradicated thanks to iodized salt, 1 in 7 Americans is believed deficient.
The association emerged from a study of more than 4,000 Dutch mothers and their children, and it supports a growing view that autism spectrum disorders can be caused by a lack of maternal thyroid hormone, which past studies have shown is crucial to the migration of fetal brain cells during embryo development.
"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.
Iodine deficiency is common throughout the world, including developed countries. The World Health Organization estimates nearly 1 in 3 people are affected globally. A 2005 CDC-University of Kansas study estimated that in the U.S., where iodine deficiency had been practically eradicated thanks to iodized salt, 1 in 7 Americans is believed deficient.