Gaps in Gestational Hypothyroidism

In 2011, the American Thyroid Association (ATA) recommended more strin­gent thyroid stimulation hormone (TSH) testing criteria. More women will now be defined as having hypothyroidism during pregnancy. A study by scien­tists at Quest Diagnostics was conducted on a national sample of 502,036 preg­nant women in the United States to determine the prevalence of gestational hypothyroidism based on the ATA’s revised guidelines. Published in the March 2012 Journal of Clinical Endocrinology & Metabolism, the analysis found that as many as 15.5% of pregnant women tested have the condition. These findings sharply contrast the widely cited hypothyroidism rates of 2.0% to 3.0% based on older, higher TSH cutoff levels. [socialpoll id=”[socialpoll id=”3362″] Assessing the Rationale The ATA revised its clinical guidelines in response to many retrospective studies that have demon­strated an association between hypothyroidism and increased risk of miscarriage, gestational hyperten­sion, and gestational diabetes as well as low birth weight and pre-term birth. Prospective clinical studies suggest even mild hypothyroidism nega­tively affects fetal brain development. “Whether TSH screening should be routine for all pregnant women is controversial, given a lack of data demonstrating if universal screening and treatment will lead to significantly improved outcomes.” Much of the data on gestational hypothyroidism has shown that both subclinical and overt hypo­thyroidism can have harmful health effects. For this reason, the ATA’s 2011 guidelines recommend assay- and trimester-specific TSH cutoffs that are significantly lower than previously recognized for detecting subclinical hypothyroidism in pregnancy. If assay-specific reference intervals are not available, the ATA recommends TSH upper thresholds of approximately 2.5 mIU/L during the first trimester and 3.0 mIU/L during the latter two trimesters. Gaps in...