Thyroid disease symptoms during early pregnancy do not identify women with thyroid hypofunction that should be...

To evaluate whether women during early pregnancy with "hypothyroidism" symptoms are at risk of biochemically defined hypothyroidism. The 2017 Guidelines of the American Thyroid Association (ATA) recommend case-finding on the basis of symptoms to identify these women during pregnancy, while evidence is lacking.

Construct validation of a thyroid hypofunction symptom checklist during the first trimester of pregnancy comparing high scores with biochemically defined hypothyroidism.

A total of 2198 healthy pregnant women from an iodine-sufficient area in 2013-2014.

Completion of a draft questionnaire with "classical" symptoms of hypothyroidism at 12 weeks of gestation. The 2.5th and 97.5th percentiles of TSH and fT4 during pregnancy in TPO-Ab-negative (<35 kU/L) women were used to define euthyroid women and those with overt (clinical) and subclinical hypothyroidism. The prevalence of overt (subclinical) hypothyroidism was compared between women with high symptom scores and those with low symptom scores.

According to fT4 and TSH cut-offs (0.23-4.0 mIU/L and 11.5-18.0 pmol/L, respectively), there were 15 women with "to treat hypofunction" (overt hypothyroidism or TSH >10 mIU/L) and 68 women with subclinical hypothyroidism. Questionnaire construct validation revealed a 12-item hypothyroid checklist with normally distributed scores. The cut-off indicating high scores of OH was set at 1 SD > mean. Women with high symptom scores did not present more often with biochemically defined thyroid hypofunction.

This study does not support the ATA recommendation that pregnant women who require levothyroxine therapy can be identified by case-based screening of women with symptoms of thyroid disease.