Update Coming for Thyroid Disease in Pregnancy Guidelines

CHICAGO — A preview of much-anticipated updates to guidelines on managing thyroid disease in pregnancy shows key changes to recommendations in the evolving field, ranging from consideration of the chance of spontaneous normalization of thyroid levels during pregnancy to a heightened emphasis on shared decision-making and the nuances can factor into personalized treatment.

The guidelines, expected to be published in early 2025, have not been updated since 2017, and with substantial advances and evidence from countless studies since then, the new guidelines were developed with a goal to start afresh, said ATA Thyroid and Pregnancy Guidelines Task Force cochair Tim IM Korevaar, MD, PhD, in presenting the final draft guidelines at the American Thyroid Association (ATA) 2024 Meeting.

“Obviously, we’re not going to ignore the 2017 guidelines, which have been a very good resource for us so far, but we really wanted to start from scratch and follow a ‘blank canvas’ approach in optimizing the evidence,” said Korevaar, an endocrinologist and obstetric internist with the Division of Pharmacology and Vascular Medicine & Academic Center for Thyroid Diseases, Department of Internal Medicine, Erasmus University Medical Center, Rotterdam, The Netherlands.

The guidelines, developed through a collaborative effort involving a wide variety of related medical societies, involved 14 systematic literature reviews. While the pregnancy issues covered by the guidelines is extensive, key highlights include:

Management in Preconception

Beginning with preconception, a key change in the guidelines will be that patients with euthyroid thyroid peroxidase (TPO) antibodies, which can be indicative of thyroid dysfunction, routine treatment with levothyroxine is not recommended, based on new evidence from randomized trials of high-risk patients showing no clear benefit from the treatment. 

“In these trials, and across analyses, there was absolutely no beneficial effect of levothyroxine in these patients [with euthyroid TPO antibody positivity],” he said. 

With evidence showing, however, that TPO antibody positivity can lead to subclinical or overt hypothyroidism within 1 or 2 years, the guidelines will recommend that TPO antibody–positive patients do have thyroid stimulating hormone (TSH) levels tested every 3-6 months until pregnancy, and existing recommendations to test during pregnancy among those patients remain in place, Korevaar reported.

In terms of preconception subclinical hypothyroidism, the guidelines will emphasize the existing recommendation “to always strive to reassess” thyroid levels, and if subclinical hypothyroidism does persist, to treat with low-dose levothyroxine.

During Pregnancy

During pregnancy, the new proposed recommendations will reflect the important change that three key risk factors, including age over 30 years, having at least two prior pregnancies, and morbid obesity (body mass index [BMI] at least 40 kg/m²), previously considered a risk for thyroid dysfunction in pregnancy, should not, on their own, suggest the need for thyroid testing, based on low evidence of an increased risk in pregnancy.

Research on the issue includes a recent study from Korevaar’s team showing these factors to in fact have low predictability of thyroid dysfunction.

“We deemed that these risk differences weren’t really clinically meaningful (in predicting risk), and so we have removed to maternal age, BMI, and parity as risk factors for thyroid testing indications in pregnancy,” Korevaar said.

Factors considered a risk, resulting in recommended testing at presentation include a history of subclinical or clinical hypo- or hyperthyroidism, postpartum thyroiditis, known thyroid antibody positivity, symptoms of thyroid dysfunction or goiter, and other factors. 

Treatment for Subclinical Hypothyroidism in Pregnancy

Whereas current guidelines recommend TPO antibody status in determining when to consider treatment for subclinical hypothyroidism, the new proposed guideline will instead recommend treatment based on the timing of the diagnosis of the subclinical hypothyroidism, with consideration of treatment during the first trimester, but not in the second or third trimester, based on newer evidence of the absolute risk for pregnancy complications and randomized trial data.

“The recommendations are now to no longer based on TPO antibody status, but instead according to the timing of the diagnosis of subclinical hypothyroidism,” Korevaar said.

Based on the collective data, “due to the low risk, we do not recommend for routine levothyroxine treatment in the second or third trimester groups with TSH levels under 10 mU/L now.” 

“However, for subclinical hypothyroidism diagnosed in the first trimester, the recommendation would be that you can consider levothyroxine treatment,” he said.

While a clear indication for treatment in any trimester is the presence of overt hypothyroidism, or TSH levels over 10 mU/L, Korevaar underscored the importance of considering nuances of the recommendations that may warrant flexibility, for instance among patients with borderline TSH levels.

Spontaneous Normalization of Thyroid Levels in Pregnancy

Another new recommendation addresses the issue of spontaneous normalization of abnormal thyroid function during pregnancy, with several large studies showing a large proportion of subclinical hypothyroidism cases spontaneously revert to euthyroidism by the third trimester — despite no treatment having been provided.

Under the important proposed recommendation, retesting of subclinical hypothyroidism is suggested within 3 weeks. 

“The data shows that a large proportion of patients spontaneously revert to euthyroidism,” Korevaar said.

“Upon identifying subclinical hypothyroidism in the first trimester, there will be essentially two options that clinicians can discuss with their patient — one would be to consider confirmatory tests in 3 weeks or to discuss the starting the lower dose levothyroxine in the first trimester,” he said.

In terms of overt hypothyroidism, likewise, if patients have a TSH levels below 6 mU/L in pregnancy, “you can either consider doing confirmatory testing within 3 weeks, or discussing with the patient starting levothyroxine treatment,” Korevaar added.

Overt Hyperthyroidism

For overt hyperthyroidism, no significant changes from current guidelines are being proposed, with the key exception of a heightened emphasis on the need for shared decision-making with patients, Korevaar said.

“We want to emphasize shared decision-making especially for women who have Graves’ disease prior to pregnancy, because the antithyroid treatment modalities, primarily methimazole (MMI) and propylthiouracil (PTU), have different advantages and disadvantages for an upcoming pregnancy,” he said.

“If you help a patient become involved in the decision-making process, that can also be very helpful in managing the disease and following-up on the pregnancy.”

Under the recommendations, PTU remains the preferred drug in overt hyperthyroidism, due to a more favorable profile in terms of potential birth defects vs MMI, with research showing a higher absolute risk of 3% vs 5%.

The guidelines further suggest the option of stopping the antithyroid medications upon a positive pregnancy test, with the exception of high-risk patients. 

Korevaar noted that, if the treatment is stopped early in pregnancy, relapse is not likely to occur until after approximately 3 months, or 12 weeks, at which time, the high-risk teratogenic period, which is between week 5 and week 15, will have passed. 

Current guidelines regarding whether to stop treatment in higher-risk hyperthyroid patients are recommended to remain unchanged.

Thyroid Nodules and Cancer

Recommendations regarding thyroid nodules and cancer during pregnancy are also expected to remain largely similar to those in the 2017 guidelines, with the exception of an emphasis on simply considering how the patient would normally be managed outside of pregnancy. 

For instance, regarding the question of whether treatment can be withheld for 9 months during pregnancy. “A lot of times, the answer is yes,” Korevaar said.

Other topics that will be largely unchanged include issues of universal screening, definitions of normal and abnormal TSH and free T4 reference ranges and isolated hypothyroxinemia.

Steps Forward in Improving Updates, Readability

In addition to recommendation updates, the new guidelines are being revised to better reflect more recent evidence-based developments and user-friendliness.

“We have now made the step to a more systematic and replicable methodology to ensure for easier updates with a shorter interval,” Korevaar told Medscape Medical News.

“Furthermore, since 2006, the ATA guideline documents have followed a question-and-answer format, lacked recommendation tables and had none or only a few graphic illustrations,” he added. 

“We are now further developing the typical outline of the guidelines to improve the readability and dissemination of the guideline document.”

Korevaar’s disclosures include lectureship fees from IBSA, Merck, and Berlin Chemie.