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New Study Will Look at Hypothyroidism in Pregnancy


Updated February 06, 2007

New Study Will Look at Hypothyroidism in Pregnancy
A government-sponsored research study is being launched with the goal of finding out if thyroid screening for all pregnant women should become a standard practice.

The study, titled "A Randomized Trial of Thyroxine Therapy for Subclinical Hypothyroidism or Hypothyroxinemia Diagnosed During Pregnancy," will enroll a total of 1,000 women who have a slightly underactive thyroid gland, and will evaluate their thyroid function during pregnancy. Half the women will receive thyroid hormone replacement and the other half will get a placebo. The children of all study participants will then be annually evaluated for developmental issues until the age of five.

According to the researchers, the purpose of the study is to evaluate the effect of thyroid treatment of women who are pregnant and diagnosed with hypothyroidism during the pregnancy, versus untreated women, in terms of the intellectual development of the child at 5 years of age.

What they are looking to find out is if failing to treat a slightly underactive thyroid during pregnancy will affect the pregnancy and impair the child intellectually. Researchers will ultimately make a determination on the controversial question of whether standardized thyroid screening and treatment for all pregnant women should be the standard of care.

Thyroid Function Critical During Pregnancy

A pregnant woman's thyroid function is crucial during pregnancy, and especially in the first trimester, when the developing baby's thyroid is unable to function and the baby depends on the mother for all the thyroid hormone essential to brain development. Babies born to significantly hypothyroid mothers who receive no treatment are at risk of serious developmental problems, including lower IQ levels, and even a condition known as cretinism, which can include severe mental retardation. Untreated hypothyroidism in the pregnant woman is also known to increase the risk of pre-term labor and stillbirth.

Studies from as far back as three years ago have shown that asymptomatic thyroid problems in a mother may have a detrimental effect on newborns. These studies are not viewed as conclusive, however, and the experts still do not agree whether treatment is warranted in pregnant women with mild hypothyroidism, where thyroid levels may be close to normal. This study hopes to clarify the question and quell the controversy, with the goal of developing a guideline.

This issue is particularly important given the large number of women suffering from thyroid disease in the U.S. While the American Association of Clinical Endocrinologists (AACE) claims that some 27 million Americans have thyroid conditions, and only half are diagnosed, the actual number is likely much larger. Using the AACE's own recommendations regarding thyroid test ranges, it's estimated that more than 50 million Americans have a thyroid condition. The majority are women, suffering from hypothyroidism.

While experts don't seem able to agree on the total number of women at risk, or whether or not to screen and treat them, experts do agree on some key facts about thyroid disease and pregnancy:

  • Women who have overt thyroid disease should be treated
  • Women who are diagnosed and treated hypothyroidism will probably need an increased dosage of thyroid medication during pregnancy, and should be periodically tested and treated
  • Women should use prenatal vitamins containing iodine, which is essential for thyroid function
If you are interested in participating in the study, find out more here.

Mary Shomon, About.com's Thyroid Guide since 1997, is a nationally-known patient advocate and best-selling author of 10 books on health, including "The Thyroid Hormone Breakthrough: Overcoming Sexual and Hormonal Problems at Every Age," "The Thyroid Diet: Manage Your Metabolism for Lasting Weight Loss," "Living Well With Hypothyroidism: What Your Doctor Doesn't Tell You...That You Need to Know," "Living Well With Graves' Disease and Hyperthyroidism," "Living Well With Autoimmune Disease," and "Living Well With Chronic Fatigue Syndrome and Fibromyalgia." Click here for more information on Mary Shomon.


Alexander, Erik. "Timing and Magnitude of Increases in Levothyroxine Requirements during Pregnancy in Women with Hypothyroidism." New England Journal of Medicine, Volume 35107/15/2004 241-249. <http://content.nejm.org/cgi/content/short/351/3/241>.

"Statement on Early Maternal Thyroidal Insufficiency: Recognition, Clinical Management and Research Directions," American Thyroid Association (ATA), April 26, 2004 <http://www.thyroid.org/professionals/publications/statements/04_04_26_maternalthyroidal.htm l>

Kooistra, Libbe, PhD et. al. "Neonatal Effects of Maternal Hypothyroxinemia During Early Pregnancy" Pediatrics, Vol. 117 No. 1 January 2006, pp. 161-167

National Institute of Child Health and Human Development, Maternal Fetal Medicine Units Network, Study Description, <http://www.bsc.gwu.edu/mfmu/Projects/brieftrl.cgi>

"Thyroid Therapy for Mild Thyroid Deficiency in Pregnancy," Clinicaltrials.gov, <http://www.clinicaltrials.gov/ct/show/NCT00388297;jsessionidBF64497FA0B249A88F223EA 13D593C63?order2>

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