New Guidelines Address Hypothyroidism Dangers in Pregnancy

[Guest guest]

Hypothyroidism during pregnancy is harmful to maternal and fetal health and

to the child's future intellectual development, according to new guidelines

of the American Thyroid

Association<http://www.liebertpub.com/contentframe.aspx?code=nh31x7M2VXcDkUK2yLH\

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reported online July 25 in

*Thyroid.* The new recommendations address the diagnosis and management of

thyroid disease during pregnancy and the postpartum period.

" Pregnancy has a profound impact on the thyroid gland and thyroid function, "

said Stagnaro-Green, MD, MHPE, from the Department of Medicine and

Obstetrics/Gynecology, Washington University School of Medicine and

Health Sciences in Washington, DC, and chair of the ATA Taskforce on Thyroid

Disease During Pregnancy and Postpartum, in a news release. " In essence,

pregnancy is a stress test for the thyroid, resulting in hypothyroidism in

women with limited thyroidal reserve or iodine deficiency. "

*Supporting Evidence*

During pregnancy, the thyroid gland may enlarge by 10% in countries where

iodine sources are sufficient, and to a greater extent in iodine-poor

countries. Production of thyroid hormones and iodine requirement each

increase by approximately 50% during pregnancy. Evidence reviewed by the

Taskforce included findings from clinical trials showing the harmful effects

of subclinical thyroid disease, as well as overt hypothyroidism and

hyperthyroidism, on pregnancy and on maternal and fetal health.

Data from ongoing studies are elucidating the association between

miscarriage and preterm delivery in women with normal thyroid function who

test positive for thyroid peroxidase (TPO) antibodies. During the first

trimester, approximately 1 in 10 pregnant women develops antibodies to TPO

or to thyroglobulin, and hypothyroidism develops in roughly 16% of these

women. The long-term effects of postpartum thyroiditis, which occurs in

approximately 33% to 50% of women with thyroid-related antibodies, are also

reviewed.

" These important guidelines were developed by a panel of international

experts representing the disciplines of endocrinology, obstetrics and

gynecology, and nurse midwives, " said ATA president A. Brent, MD,

professor of medicine and physiology at the Geffen School of Medicine,

University of California Los Angeles. " This broad representation of

providers that care for pregnant women will significantly increase the

impact of these guidelines and translation of findings from the most recent

research to clinical practice. "

*ATA Recommendations*

The new guidelines include 76 specific recommendations highlighting the role

of thyroid function tests, hypothyroidism, thyrotoxicosis, iodine, thyroid

antibodies and miscarriage/preterm delivery, thyroid nodules and cancer,

postpartum thyroiditis, recommendations on screening for thyroid disease

during pregnancy, and areas for future research.

Among the specific recommendations are the following:

- Oral levothyroxine is indicated for women with overt hypothyroidism,

which is associated with greater risks for fetal loss and premature birth,

and for those with subclinical hypothyroidism who test positive for TPO

antibodies.

- To treat maternal hypothyroidism, use of triiodothyronine, desiccated

thyroid, or other thyroid preparations is strongly recommended against.

- Women who are already receiving thyroid replacement therapy should

increase their dose by 25% to 30% when they become pregnant.

- Women with subclinical hypothyroidism in pregnancy who are not

initially treated should be monitored for progression to overt

hypothyroidism. Serum thyroid-stimulating hormone (TSH) and free thyroxine

(FT4) levels should be measured approximately every 4 weeks until 16 to

20 weeks' gestation and at least once between 26 and 32 weeks' gestation.

- In the first trimester, normal range for TSH level is 0.1 to 2.5 mIU/L;

this level increases to 0.2 to 3.0 mIU/L in the second trimester and 0.3 to

3.0 mIU/L in the third trimester.

- Serum levels of FT4 during pregnancy should be measured with online

solid phase extraction-liquid chromatography, or tandem mass spectrometry on

serum dialysate or ultrafiltrate.

- Treatment is not needed for women with isolated low FT4 levels.

- During pregnancy and lactation, the minimal suggested daily recommended

allowance for iodine is 250 ìg. The risk for fetal hypothyroidism may

increase when total daily iodine intake from diet and/or supplements is or

exceeds 500 ìg.

- Pregnant women should not undergo radioactive iodine thyroid scanning,

but fine-needle aspiration of thyroid nodules may be performed if indicated.

- Evidence is insufficient to recommend for or against routine screening

for antithyroid antibodies among women with miscarriage, or universal TSH

screening in the first trimester. However, screening for FT4 level is not

recommended.

- Antithyroid drugs are not indicated for gestational hyperthyroidism,

which can be managed supportively. However, women in the first trimester in

whom Graves' hyperthyroidism develops should receive propylthiouracil.

- During the thyrotoxic phase of postpartum thyroiditis, antithyroid

drugs are not needed. To monitor women for development of hypothyroidism

once the thyrotoxic phase has ended, screening should be performed every 2

months for 1 year.

- At approximately 6 to 12 months after starting treatment of postpartum

thyroiditis for their patients, clinicians should try to taper thyroid

replacement therapy.

" Thyroid disease in pregnancy is common, clinically important, and

time-sensitive, and our knowledge about it is rapidly changing, " said ATA

secretary/chief operating officer T. Kloos, MD, professor at Ohio

State University. " This ATA Guideline will disseminate this new information

both widely and rapidly to improve patient care, establish what we believe

is optimal care for the pregnant woman and her unborn child, and drive

future research to further improve our understanding and patient outcomes. "

*The authors of the guidelines have disclosed no relevant financial

relationships.*

*Thyroid.* Published online July 25,

2011.<http://www.liebertpub.com/contentframe.aspx?code=nh31x7M2VXcDkUK2yLHKgCdvv\

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