Autoimmune Thyroid Disease and Pregnancy Workup

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

Laboratory Studies

Hyperthyroidism

  • T3, T4, FT3, FT4, and TSH tests
    • Total T3 and total T4 levels are increased due to a rise in the amount of thyroid-binding globulin. Free T3 (FT3) and FT4 levels are high-normal in the first trimester and return to normal by the second trimester.
    • Total T4 values are not useful in pregnant women because they rise in response to the estrogen-induced increase in the amount of thyroid-binding globulin.
    • FT3 values should be measured when the TSH value is suppressed but the FT4 level is normal. An elevated T3 level confirms T3 toxicosis.
    • TSH concentrations fall during pregnancy, especially in the first trimester, because hCG cross-reacts with TSH receptors on the thyroid gland.
      • In a prospective study of 666 women in Belgium, suppressed TSH levels were noted in 15%, 10%, and 5% in first-, second-, and third-trimester pregnancies.[9]
      • Trimester-specific TSH normograms have been described. TSH levels are significantly lower and FT4 levels are significantly higher in the first trimester than levels in the second or third trimesters.
    • TSH levels alone should not be used to diagnose hyperthyroidism in pregnancy.
    • The FT4 index is slightly low or normal.
    • Among patients in a hyperthyroid state, the TSH level is low, whereas the FT4 or FT4 index value is elevated.
  • Resin T3 update test: Resin T3 uptake is reduced because the number of unsaturated binding sites increases.
  • Test for thyroid-stimulating immunoglobulins
    • Patients with Graves disease almost always have positive results for thyroid-stimulating immunoglobulins (TSIs).
    • Measurement of TSI concentrations should be part of the workup for patients with hyperthyroidism.
  • CBC, liver function test, and determination of calcium and magnesium levels
    • These laboratory tests should be ordered after hyperthyroidism is diagnosed.
    • Findings or conditions that can occur with hyperthyroidism include normochromic normocytic anemia, mild neutropenia, elevated liver enzyme levels, mild hypercalcemia, and hypomagnesemia.
  • Antimicrosomal antibody test: Women who have positive results for antimicrosomal antibodies early in pregnancy or shortly after delivery are at risk for developing PPT.

Hypothyroidism

  • FT4 and TSH tests
    • In primary hypothyroidism, TSH levels are elevated and the FT4 value or FT4 index should be low.
    • With suprathyroid hypothyroidism, the TSH level may be normal or low, and the FT4 level or FT4 index is low.
    • In subclinical hypothyroidism, the FT4 value is normal, and the TSH level is elevated.
  • Tests for anti-TPO and antithyroglobulin antibodies
    • levels of anti-TPO and antithyroglobulin antibodies should be measured in pregnant women with possible hypothyroidism to determine if Hashimoto thyroiditis is the cause.
    • Measurement of anti-TPO antibody concentrations is often sufficient because the results are almost always positive in patients with Hashimoto thyroiditis.
  • CBC and liver function tests
    • Consider ordering a CBC and liver function tests after hypothyroidism is diagnosed.
    • Anemia is observed in as many as 30-40% of patients because erythropoiesis is decreased.
    • Concomitant vitamin B-12 or folic acid deficiency should be considered if the anemia is macrocytic.
    • Leukocyte and platelet counts are usually normal.
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Imaging Studies

Imaging modalities currently available for the evaluation of thyroid disease are ultrasonography, CT scanning, MRI, and radioactive iodine uptake testing. Radioactive iodine uptake testing is contraindicated in pregnancy. Ultrasonography is considered a safe test in pregnancy, and sonographic findings can help in differentiating a cystic nodule from a solid nodule.

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Procedures

Thyroid biopsy is rarely necessary for diagnosing autoimmune thyroid disease in pregnant women.

The workup of a thyroid nodule should not be delayed in pregnancy. Fine-needle aspiration biopsy can provide valuable cytologic information.

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Histologic Findings

The essential histologic findings of Graves disease are glandular hyperplasia and hypertrophy characterized by increased height of the follicular cells and redundancy of the follicular wall. Lymphocytic infiltration reflects the immune aspect of this disease.

Ophthalmopathy of Graves disease is characterized by lymphocytic infiltration of the orbital contents with lymphocytes, mast cells, and plasma cells. Likewise, lymphocytic infiltration is readily observed in association with the dermal thickening seen in the dermopathy found in patients with Graves disease.

Hashimoto thyroiditis is characterized by extensive diffuse lymphocytic infiltration. Other classic findings are follicular rupture, eosinophilia, various degrees of hyperplasia, and fibrosis.

PPT is characterized by destructive lymphocytic infiltration of the thyroid gland.

See also Pathophysiology.

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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
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