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TOPLINE:

Individuals with subclinical hypothyroidism, thyroid peroxidase antibodies, or both during pregnancy were more likely to develop overt hypothyroidism over the following decades than those with normal thyroid function.

METHODOLOGY:

• Researchers conducted a retrospective cohort study to assess long-term progression to overt hypothyroidism after the identification of thyroid abnormalities during pregnancy.
• They identified pregnant individuals who had thyroid-stimulating hormone and free thyroxine levels measured before 20 weeks of pregnancy in a Dallas public health system between 2000 and 2003.
• The analysis included 718 individuals (mean age, 25.8-27.5 years), of whom 108 had subclinical hypothyroidism, 455 had thyroid peroxidase antibodies, and 155 had both conditions.
• In a nested analysis, 118 individuals with antenatal thyroid abnormalities were matched with an equal number of control individuals without such abnormalities.
• The primary outcome was the cumulative incidence of overt hypothyroidism.

TAKEAWAY:

• Over a median follow-up of about 21 years, 33.1% of individuals experienced progression to overt hypothyroidism.
• Progression occurred in 25% of those with subclinical hypothyroidism, 28.4% with thyroid peroxidase antibodies, and in 52.9% with both abnormalities (P < .001).
• In the nested analysis, individuals with antenatal thyroid abnormalities were nearly threefold more likely to progress to overt hypothyroidism than matched control individuals (28.8% vs 10.2%; P < .001) and did so sooner (mean, 10.7 vs 15.5 years; P = .02). 

IN PRACTICE:

“Individuals identified with subclinical hypothyroidism or thyroid peroxidase antibodies during pregnancy carry meaningful long-term risk of overt thyroid failure, independent of background population risk. While the current data do not support a specific surveillance interval, the antenatal thyroid phenotype provides a practical basis for risk stratification,” the researchers wrote.

SOURCE:

The study was led by Christine Henricks, DO, of the University of Texas Southwestern Medical Center in Dallas. It was published online on May 27 in the American Journal of Obstetrics and Gynecology.

LIMITATIONS:

Follow-up was limited to care within one health system. Thyroid tests were done for all women instead of the risk-based screening currently practiced.

DISCLOSURES:

The study did not receive any funding. Two authors reported receiving royalties from McGraw-Hill Publishing, and one also reported receiving royalties from Wolters Kluwer. Another author reported serving as an editor for the American Journal of Obstetrics and Gynecology. 

This article was created using several editorial tools, including AI, as part of the process. Human editors reviewed this content before publication.