ATA Guidelines Tools

24 Subclinical Hyperthyroidism and Pregnancy 96. The ATA suggests that the physician contacted according to Rec. 95 evaluate whether ATD withdrawal in the first trimester of pregnancy is likely to cause relapse of hyperthyroidism. (W-L) • Evaluation should be based on patient records, especially the severity of GD at time of diagnosis and current disease activity, duration of ATD therapy, current ATD dose requirement, and results of recent thyroid function and TRAb testing. • If risk of relapse is considered low, therapy can be withdrawn, and followed by weekly thyroid function testing during the 1st trimester. 97. The ATA suggests that women in early pregnancy who have a high risk of recurrent or worsening hyperthyroidism if ATD is withdrawn be shifted from MMI to PTU immediately after diagnosing pregnancy. (W-L) 98. Women taking PTU during the 1st trimester of pregnancy according to Recs. 90, 93 & 97 may be switched to MMI at the beginning of the 2nd trimester, or they may continue PTU therapy for the remaining part of pregnancy if ATD is needed. (N-In) 99. GD during pregnancy should be treated with the lowest possible dose of ATD needed to keep the mother's thyroid hormone levels at or slightly above the reference range for total T 4 and T 3 values in pregnancy (1.5 times above non-pregnant reference ranges in the 2nd and 3rd trimester), and the TSH below the reference range for pregnancy. Similarly, free T 4 levels should be kept at or slightly above the upper limit of the pregnancy trimester reference range for the assay. (S-L) • Thyroid function should be assessed at least monthly, and the ATD dose adjusted, as required. 100. Pregnancy is a relative contraindication to thyroidectomy and should only be used when medical management has been unsuccessful or ATDs cannot be used. (S-L) 101. When thyroidectomy is necessary for the treatment of hyperthyroidism during pregnancy, the surgery should be performed if possible during the second trimester. (S-L) 102. TRAb levels should be measured when the etiology of hyperthyroidism in pregnancy is uncertain. (S-L) 103. Patients who were treated with RAI or thyroidectomy for GD prior to pregnancy should have TRAb levels measured using a sensitive assay initially during the first trimester thyroid function testing and, if elevated, again at 18–22 weeks of gestation. (S-L)

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