Hypothyroidism in Pregnancy Linked to ADHD in Children

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Your thyroid hormone is a chemical messenger that goes from your thyroid, through your placenta, to your developing baby. Thyroid hormone is essential for developing babies, especially in the first three months of pregnancy. Low thyroid hormone – hypothyroidism – has been linked to many pregnancy risks and has also been linked to attention-deficit hyperactivity disorder (ADHD) in children born to mothers with hypothyroidism. You can read  more about the effects of thyroid disease in pregnancy here.

The first large-scale, long-term study to investigate how hypothyroidism during pregnancy affects the risk of ADHD in children was recently published in the American Journal of Perinatology. The study comes from researchers at NYU School of Medicine and NYU Langone Health. This study is important because it found that hypothyroidism is more of a risk for ADHD than previously believed.

The Study

This study followed over 300,000 children from birth to age 17. Close to 17,000 of these children were diagnosed with ADHD over 17 years. Thyroid levels of their mothers were available just before and during pregnancy. These levels were used to investigate how much hypothyroidism might contribute to the risk for ADHD. These are the key findings:

  • Children of women with hypothyroidism just before or early in a pregnancy had a 24 percent higher risk of ADHD than children of women who were not hypothyroid.
  • ADHD risk was highest in the first trimester. After the first three months of pregnancy, a developing baby starts to make its own thyroid hormones. Hypothyroidism after three months had little effect on ADHD risk.
  • Male children of hypothyroid women were at higher risk than female children. This is not surprising since ADHD is more common in boys.
  • Hispanic children were at higher risk than any other ethnic group. This was surprising. Compared to white children, their ADHD risk was about 20 percent higher.

What Might This Study Mean for You?

About 18 percent of women are at risk for significant hypothyroidism during pregnancy. You may be at risk if you have a personal or family history of thyroid disease. Being over age 30, having an autoimmune disease, a history of infertility, or being overweight may also put you at risk. Before or early in pregnancy, talk to your doctor about your thyroid health. Ask your doctor if you are at risk and let your doctor know if you have symptoms of hypothyroidism like, fatigue, weakness, weight gain, sensitivity to cold, dry skin, hair loss, or constipation.

There is an ongoing debate on whether it is worthwhile to do routine thyroid hormone screening before or in early pregnancy. Both the American College of Obstetricians and Gynecologists and the American Thyroid Association recommend screening women at high risk and support screening for all women.

ADHD is the most common brain development disorder in children. This large and long-term study underlines the importance of monitoring thyroid hormone levels in women before and during pregnancy. Babies of women who do have hypothyroidism in early pregnancy should be followed for possible development of ADHD symptoms like inability to focus attention and hyperactivity. Early diagnosis of ADHD in children makes ADHD easier to manage, according to several studies.

The researchers conclude that thyroid health in pregnant women may be more important for fetal brain development than previously realized. The researchers plan to continue investigating  hypothyroidism during pregnancy and its possible link to other brain developmental diseases like epilepsy and cerebral palsy.

Christopher Iliades
Dr. Chris Iliades is a medical doctor with 20 years of experience in clinical medicine and clinical research. Chris has been a full time medical writer and journalist since 2004. His byline appears in over 1,000 articles online including EverydayHealth, The Clinical Advisor, and Healthgrades. He has also written for print media including Cruising World Magazine, MD News, and The Johns Hopkins Children's Center Magazine. Chris lives with his wife and close to his three children and four grandchildren in the Boston area.

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