New Guidelines: Thyroid Disease during Pregnancy

New Guidelines: Thyroid Disease during Pregnancy

The Endocrine Society’s clinical practice guideline for the management of thyroid disease during pregnancy and after birth has been updated from its 2007 version. [August issue of the Journal of Clinical Endocrinology and Metabolism]

Diagnosing and treating patients with thyroid-related medical issues before, during, and immediately after pregnancy.

• Trimester-specific reference ranges for pregnant women, using a free T₄ assay, should be established.
• The nonpregnant total T₄ range (5–12 μg/dL or 50–150 nmol/liter) can be adapted in the second and third trimesters by multiplying this range by one and a half-fold.
• Free T₄ index appears to be a reliable assay during pregnancy.
• Propylthiouracil (PTU) should be the first-line drug for treatment of hyperthyroidism during the first trimester of pregnancy.
•  Methimazole (MMI) may also be prescribed if PTU is not available or not tolerated.

• Clinicians should change treatment of patients from PTU to MMI after completion of the first trimester because of the potential for liver toxicity.
• Breast-feeding women should maintain a daily intake of 250 μg iodine to ensure breast-milk provides 100 μg iodine per day to the infant.
• Once-daily prenatal vitamins should contain from 150 to 200 μg iodine in the form of potassium iodide or iodate
• Thyroid receptor antibodies should be measured before 22 weeks’ gestational age in mothers with “1) current Graves’ disease; or 2) a history of Graves’ disease and treatment with ¹³¹I or thyroidectomy before pregnancy; or 3) a previous neonate with Graves’ disease or 4) previously elevated [thyroid-stimulating hormone receptor antibodies (TRAb)].
• In women with TRAb at least 2- to 3-fold the normal level and women treated with antithyroid drugs, fetal thyroid dysfunction should be screened for during the fetal anatomy ultrasound done in the 18th–22nd week and repeated every four to six weeks or as clinically indicated.
• Evidence of fetal thyroid dysfunction could include thyroid enlargement, growth restriction, hydrops, presence of goiter, advanced bone age, tachycardia, or cardiac failure.
• Women with nodules from 5 mm to 1 cm in size should be considered for fine-needle aspiration (FNA) if they have a high risk history or suspicious findings on ultrasound, and women with complex nodules from 1.5 to 2 cm in size should also receive an FNA. “During the last weeks of pregnancy, FNA can reasonably be delayed until after delivery. Ultrasound-guided FNA is likely to have an advantage for maximizing adequate sampling,”