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Endocrine Society revises recommendations for thyroid disease during pregnancy, postpartum
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The Endocrine Society has revised its 2007 Clinical Practice Guideline on the management of thyroid disease in pregnant and postpartum women. Updates include recommendations regarding diagnosis and treatment before, during and after pregnancy.
“Pregnancy may affect the course of thyroid diseases, and conversely, thyroid diseases may affect the course of pregnancy,” Leslie De Groot, MD, a researcher from the University of Rhode Island, said in a press release. “Pregnant women may be under the care of multiple health care professionals, including obstetricians, nurse midwives, family practitioners and endocrinologists, making the development of guidelines all the more critical.”
Key updates
According to the release, revisions include:
- Caution should be used in the interpretation of serum free thyroxine levels during pregnancy and each laboratory should establish trimester-specific reference ranges for pregnant women using a free T4 assay. The non-pregnant total T4 range (5 mcg/dL to 12mcg/dL or 50 nmol/L to 150 nmol/L) can be adapted in the second and third trimesters by multiplying this range by 1.5-fold. Alternatively, the free T4 index appears to be a reliable assay during pregnancy.
- Propylthiouracil (PTU), if available, should be the first-line drug for treatment of hyperthyroidism during the first trimester of pregnancy because of the possible association of methimazole (Tapazole, King Pharma) with congenital abnormalities. Methimazole may also be prescribed if PTU is not available or if a patient cannot tolerate or has an adverse response to PTU. Recent analyses by the FDA indicate that PTU may rarely be associated with severe liver toxicity. For this reason, clinicians should change treatment of patients from PTU to methimazole after completion of the first trimester.
- Breast-feeding women should maintain a daily intake of 250 mcg of iodine to ensure breast milk provides 100 mcg of iodine per day to the infant.
- Once-daily prenatal vitamins should contain 150 mcg to 200 mcg iodine in the form of potassium iodide or iodate — the content of which is verified to ensure that all pregnant women taking prenatal vitamins are protected from iodine deficiency.
- Since thyroid receptor antibodies (thyroid receptor stimulating, binding or inhibiting antibodies) freely cross the placenta and can stimulate or inhibit the fetal thyroid, these antibodies should be measured before 22 weeks gestational age in mothers with 1) current Graves’ disease; 2) a history of Graves’ disease and treatment with radioactive iodine (I-131) or thyroidectomy before pregnancy; 3) a previous neonate with Graves’ disease; or 4) previously elevated thyroid-stimulating hormone receptor antibodies.
- In women with thyroid-stimulating hormone receptor antibodies, at least two- to threefold the normal level and women treated with antithyroid drugs, fetal thyroid dysfunction should be screened for during the fetal anatomy ultrasound (18 to 22 weeks) and repeated every 4 to 6 weeks or as clinically indicated. Evidence of fetal thyroid dysfunction could include thyroid enlargement, growth restriction, hydrops, presence of goiter, advanced bone age or cardiac failure.
- Women with nodules ranging 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. Women with complex nodules ranging from 1.5 cm to 2 cm in size should also receive an FNA. During the last 6 weeks of pregnancy, FNA can reasonably be delayed until after delivery. Ultrasound-guided FNA is likely to have an advantage for maximizing adequate sampling.
Up for debate
The committee charged with updating the guidelines, however, did not reach a consensus on screening recommendations for all newly pregnant women. For instance, some members recommended screening all pregnant women for serum TSH abnormalities by the ninth week or at the time of their visit, whereas others supported aggressive case finding to identify and test high-risk women.
A full summary of the changes between the 2007 and the 2012 recommendations can be found in the August issue of the Journal of Clinical Endocrinology and Metabolism.
Disclosure: Several researchers are members of the American Thyroid Association and other associations. The researchers report no relevant financial disclosures.
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