Autoimmune Thyroid Disease and Pregnancy Treatment & Management

  • Author: Dotun A Ogunyemi, MD; Chief Editor: Carl V Smith, MD   more...
 
Updated: Mar 8, 2012
 

Medical Care

Hyperthyroidism

The goal of treatment is to maintain clinical euthyroidism, with the mother's FT4 level in the high-normal range.

Thioamide drugs (ie, ATDs) are the first-line treatment in pregnancy. PTU, methimazole (MMI), and carbimazole (CMI) are the ATDs available in the United States. These drugs inhibit iodination of thyroglobulin and thyroglobulin synthesis by competing with iodine for the enzyme peroxidase. PTU, MMI, and CMI are equally effective.

A controversial association exists between MMI and fetal scalp defects, aplastic cutis, and choanal and/or esophageal atresia. Therefore, PTU tends to be the first choice in this class of drugs.

The US Food and Drug Administration (FDA) had added a boxed warning, the strongest warning issued by the FDA, to the prescribing information for propylthiouracil. The boxed warning emphasizes the risk for severe liver injury and acute liver failure, some of which have been fatal. The boxed warning also states that propylthiouracil should be reserved for use in those who cannot tolerate other treatments such as methimazole, radioactive iodine, or surgery.

The decision to include a boxed warning was based on the FDA's review of postmarketing safety reports and meetings held with the American Thyroid Association, the National Institute of Child Health and Human Development, and the pediatric endocrine clinical community.

The FDA has identified 32 cases (22 adult and 10 pediatric) of serious liver injury associated with propylthiouracil (PTU). Of the adults, 12 deaths and 5 liver transplants occurred, and among the pediatric patients, 1 death and 6 liver transplants occurred. PTU is indicated for hyperthyroidism due to Graves disease.[10]

These reports suggest an increased risk for liver toxicity with PTU compared with methimazole. Serious liver injury has been identified with methimazole in 5 cases (3 resulting in death). PTU is considered as a second-line drug therapy, except in patients who are allergic or intolerant to methimazole, or for women who are in the first trimester of pregnancy. Rare cases of embryopathy, including aplasia cutis, have been reported with methimazole during pregnancy.

The FDA recommends the following criteria be considered for prescribing PTU. For more information, see the FDA Safety Alert.

  • Reserve PTU use during first trimester of pregnancy, or in patients who are allergic to or intolerant of methimazole.
  • Closely monitor PTU therapy for signs and symptoms of liver injury, especially during the first 6 months after initiation of therapy.
  • For suspected liver injury, promptly discontinue PTU therapy and evaluate for evidence of liver injury and provide supportive care.
  • PTU should not be used in pediatric patients unless the patient is allergic to or intolerant of methimazole, and no other treatment options are available.
  • Counsel patients to promptly contact their health care provider for the following signs or symptoms: fatigue, weakness, vague abdominal pain, loss of appetite, itching, easy bruising, or yellowing of the eyes or skin.

Doses of ATDs should be maintained at the lowest dose needed to keep the mother's FT4 level in the high-normal range. Weight gain, pulse rate, FT4 results, and TSH levels should be monitored monthly.

Beta-blockers (eg, atenolol, nadolol, propranolol) are valuable adjuncts to ATDs. These drugs effectively alleviate symptoms of hypermetabolic states. With prolonged use, beta-blockers are associated with fetal morbidity. Therefore, these drugs should be used for only a short period (ie, 2 wk) while one waits for the ATDs to take effect.

Iodide decreases serum T4 and T3 levels by 30-50% in 10 days. Iodide is used in combination with ATDs and beta-blockers during the preoperative treatment of patients with hyperthyroidism. Iodide can also be used in the medical treatment of patients with thyroid storm. Fetal hypothyroidism resulting from placental passage is reported with prolonged use of iodide products; therefore, iodide use should be limited to less than 2 weeks.

Use of radioactive iodine is contraindicated in pregnancy.

Hypothyroidism

The goal of treatment is to normalize maternal TSH levels. It should be remembered that iodine deficiency is an important cause of neonatal neurologic damage worldwide. The recommended mean intake of iodine during pregnancy and lactation is approximately 250 mcg/d.

Thyroid hormone replacement is the treatment for patients with hypothyroidism, which should be corrected before pregnancy occurs. A full replacement dosage of 1.7-2.0 mcg/kg/d should be started at the time of diagnosis. Preconception thyroid medication should be adjusted to achieve a TSH level of less than 2.5 mU/mL before pregnancy.

The dosage of thyroid hormone should be increased at 4-6 weeks of gestation; an increase of 30-50% may be required. In general, adjustments are made as shown in the Table below.

Table. Mean Increases in Dosages of Thyroid Hormone According to Serum TSH levels (Open Table in a new window)

Serum TSH level,



mIU/mL or mIU/L



Increase,



mcg/d



5-1025-50
10-2050-75
< 2075-100

If hypothyroidism is diagnosed during pregnancy, the thyroid medication should be titrated rapidly to achieve TSH levels of less than 2.5 mcg. During pregnancy, the full replacement dosage of T4 is approximately 2.0-2.4 mcg/kg/d.

Results of thyroid function tests (TFTs) should be checked within 30 days after the dosage is changed. TFTs should be repeated until the results return to normal. Afterward, levels may be checked 6-8 weeks.

Patients with subclinical hypothyroidism should be treated to normalize maternal TSH levels. Women with thyroid antibodies in pregnancy who are euthyroid should be monitored with TFTs because of their high risk of developing hypothyroidism.

After delivery, the dosage of thyroid medication usually needs to be decreased over 4 weeks.

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Surgical Care

Hyperthyroidism

Subtotal thyroidectomy induces remission in most patients with Graves disease. Surgery should be used as the second line of treatment in pregnant women.

Surgery is reserved for patients who meet 1 of the following criteria:

  • High doses of ATDs (PTU > 300 mg, MMI > 20 mg) are required.
  • Clinical hyperthyroidism cannot be controlled.
  • Fetal hypothyroidism occurs at the dosage needed for maternal control.
  • The patient cannot tolerate ATDs.
  • The patient is noncompliant.
  • Malignancy is suspected.

When surgery is needed, it should be performed during the second trimester.

Hypothyroidism

No surgical care is recommended.

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Consultations

Consultation with perinatologists and endocrinologists is recommended.

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Contributor Information and Disclosures
Author

Dotun A Ogunyemi, MD  Associate Professor of Obstetrics and Gynecology, David Geffen School of Medicine at UCLA; Residency Program Director, Clerkship Director, Department of Obstetrics and Gynecology, Cedars Sinai Medical Center

Dotun A Ogunyemi, MD is a member of the following medical societies: American College of Obstetricians and Gynecologists, American Institute of Ultrasound in Medicine, American Medical Association, National Medical Association, and Society for Maternal-Fetal Medicine

Disclosure: Nothing to disclose.

Specialty Editor Board

Francisco Talavera, PharmD, PhD  Adjunct Assistant Professor, University of Nebraska Medical Center College of Pharmacy; Editor-in-Chief, Medscape Drug Reference

Disclosure: Medscape Salary Employment

Carl V Smith, MD  The Distinguished Chris J and Marie A Olson Chair of Obstetrics and Gynecology, Professor, Department of Obstetrics and Gynecology, Senior Associate Dean for Clinical Affairs, University of Nebraska Medical Center

Carl V Smith, MD is a member of the following medical societies: American College of Obstetricians and Gynecologists, American Institute of Ultrasound in Medicine, Association of Professors of Gynecology and Obstetrics, Central Association of Obstetricians and Gynecologists, Council of University Chairs of Obstetrics and Gynecology, Nebraska Medical Association, and Society for Maternal-Fetal Medicine

Disclosure: Nothing to disclose.

Frederick B Gaupp, MD  Consulting Staff, Department of Family Practice, Hancock Medical Center

Frederick B Gaupp, MD is a member of the following medical societies: American Academy of Family Physicians

Disclosure: Nothing to disclose.

Chief Editor

Carl V Smith, MD  The Distinguished Chris J and Marie A Olson Chair of Obstetrics and Gynecology, Professor, Department of Obstetrics and Gynecology, Senior Associate Dean for Clinical Affairs, University of Nebraska Medical Center

Carl V Smith, MD is a member of the following medical societies: American College of Obstetricians and Gynecologists, American Institute of Ultrasound in Medicine, Association of Professors of Gynecology and Obstetrics, Central Association of Obstetricians and Gynecologists, Council of University Chairs of Obstetrics and Gynecology, Nebraska Medical Association, and Society for Maternal-Fetal Medicine

Disclosure: Nothing to disclose.

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Table. Mean Increases in Dosages of Thyroid Hormone According to Serum TSH levels
Serum TSH level,



mIU/mL or mIU/L



Increase,



mcg/d



5-1025-50
10-2050-75
< 2075-100
Previous
Next
 
 
 
 
 
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