ATA Releases New Guidelines on Thyroid Disease in Pregnancy

Veronica Hackethal, MD

January 12, 2017

The American Thyroid Association (ATA) has released new guidelines on the diagnosis and management of thyroid disease in pregnancy and the postpartum period. The 192 pages of recommendations were published online January 6 in Thyroid.

"With an estimated 300,000 pregnancies impacted by thyroid disease in the United States annually, these guidelines coalesce the best available evidence into clear clinical recommendations and will improve the health of many, many mothers and newborns alike," task force cochairs Erik K Alexander MD, Brigham and Women's Hospital and Harvard Medical School, Boston, Massachusetts, and Elizabeth N Pearce, MD, MSc, Boston University School of Medicine, say in an ATA press release.

The guidelines update those made in 2011 and include 97 recommendations about the management of thyroid disorders during pregnancy and postpartum.

They also include new sections not present in past recommendations, covering thyroid disease during lactation, thyroid dysfunction in women with infertility, and fetal and neonatal implications of maternal thyroid disease.

Recognizing a wealth of new data that has accumulated since 2011, the ATA created an international task force of experts in thyroidology to update the guidelines. The task force conducted a literature review of studies published in English since 1990 and a selective review of seminal studies published before 1990. They also used past guidelines and input from stakeholders and task-force members to inform the new recommendations.

In addition to the new sections, the guidelines cover thyroid-function testing, iodine nutrition, thyroid antibodies and pregnancy complications, treatment of thyroid disease during pregnancy, hypothyroidism in pregnancy, thyrotoxicosis in pregnancy, thyroid nodules and cancer in pregnancy, screening for thyroid dysfunction in pregnancy, and future research needs.

Thyroid-Function Tests Need to Be Interpreted Differently in Pregnancy

"An important point about the guidelines is that thyroid-function tests need to be interpreted differently in pregnant women than outside the setting of pregnancy," Dr Pearce told Medscape Medical News. The definition of what is "normal" changes because of thyroid physiology in pregnancy, she explained.

And defining the upper limit of normal for TSH in pregnant women has been controversial, she acknowledged.

But the "huge amount" of new data about normal pregnancy reference ranges has allowed for a revision of how to interpret TSH in pregnant women, she explained.

Treatment of Hyperthyroidism in Pregnancy is "Challenging"

Another major point: new data suggest neither methimazole (MMI) nor propyl thiouracil (PTU) is completely safe in pregnancy. MMI was previously known to cause birth defects, but new research suggests both drugs pose risks.

That makes treating overt hyperthyroidism, or Graves' disease, in pregnancy challenging. Not treating significant hyperthyroidism causes risk to the mother and the fetus.

But in the first trimester, which is the period of organ development, treatment with MMI or PTU may also pose some risk, Dr Pearce explained.

"When Graves is diagnosed before pregnancy, we are really trying to advocate for a very nuanced discussion about risks and benefits. So that a woman has a game plan in place when she does become pregnant and so that she might consider definitive therapy — getting rid of a functional thyroid — prior to pregnancy," she emphasized.

Still No Clear Consensus on Managing Subclinical Hypothyroidism

The guidelines also cover several other controversial areas, including how to manage subclinical hypothyroidism in pregnancy.

"That remains very unclear based on data. We have provided new process-based recommendations, but I will say the data are still not definitive in that area," Dr Pearce said.

Overt hypothyroidism, on the other hand, needs to be treated anytime it presents in pregnancy, she stressed, because adequate thyroid hormone is needed for pregnancy and normal fetal brain development.

"Ideally, overt hypothyroidism should be optimally treated before a woman becomes pregnant. But even when it is optimally treated with levothyroxine before pregnancy, dose adjustments will likely be needed during gestation," she said.

Another controversial area concerns universal screening for thyroid dysfunction in pregnant women.

"We did not change recommendations from prior guidelines. We don't have enough evidence to recommend for or against screening," Dr Pearce said.

The guidelines were funded by the American Thyroid Association. Dr Pierce has been a consultant for the Scientific Consulting Company. Dr Alexander has been a consultant for Veracyte . Disclosures for the coauthors are listed in the paper.

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Thyroid. Published online January 6, 2017. Article

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