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Thyroid Disorders in Pregnancy

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Definition

The thyroid is a butterfly-shaped gland located in the front of the neck. It produces hormones that control metabolism. Pregnancy hormones can affect thyroid hormones. Untreated thyroid disorders in pregnancy increase the risk of pregnancy complications. It may cause harm to the developing fetus. There are two types of thyroid disorders:

  • Hypothyroidism —the thyroid gland does not produce enough thyroid hormone
  • Hyperthyroidism —the thyroid gland produces too much thyroid hormone
The Thyroid Gland
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Causes

Hypothyroidism

Hashimotos disease is the most common cause of hypothyroidism. The immune system attacks the thyroid gland. Other causes of hypothyroidism in pregnancy include:

  • Inadequate treatment of pre-existing hypothyroidism
  • Overtreatment of hyperthyroidism

Hyperthyroidism

Graves disease is characterized by overactivity of the thyroid. It is the most common cause of hyperthyroidism. Another cause of hyperthyroidism in pregnancy is very high levels of human chorionic gonadotropin (hCG). However, cases of high hCG can resolve on their own.

Risk Factors

Factors that increase your chance of developing a thyroid disorder include:

Symptoms

Symptoms of hypothyroidism may include:

  • Goiter in the front of your neck
  • Fatigue
  • Forgetfulness
  • Depression
  • Dry skin
  • Slow heartbeat
  • Weight gain
  • Constipation
  • Intolerance to cold

Untreated hypothyroidism in pregnancy can:

  • Increase the risk of miscarriage and fetal death
  • Preeclampsia
  • Low birth weight

Symptoms of hyperthyroidism may include:

  • Unexplained weight loss
  • Heart palpitations or abnormal heart rhythm
  • Sweating
  • Nervousness
  • Tremors
  • Protruding eyes
  • Intolerance to heat
  • Diarrhea
  • Trouble sleeping

Untreated hyperthyroidism in pregnancy is associated with:

  • Heart failure
  • Premature birth and low birth weight
  • Preeclampsia
  • Stillbirth
  • Fetal hyperthyroidism

Diagnosis

Your doctor will ask about your symptoms and medical history. A physical exam will be done.

Your doctor will test your thryoid hormone levels and other blood tests. Imaging of the thyroid may also be done. You may be referred to a doctor who specializes in hormone disorders.

Treatment

Hypothyroidism

To treat hypothyroidism, your doctor will prescribe medication to replace the hormone your thyroid is not producing enough of.

Hyperthyroidism

Mild hyperthyroidism during pregnancy is often monitored closely without therapy. In some cases, you may need to take medication. If antithyroid medications do not work, surgical removal of your thyroid gland may be done. It is rarely recommended during pregnancy. Treatment with radioiodine destroys the thyroid gland. It is not done during pregnancy because of risk to the fetus.

Hormones associated with pregnancy can cause changes in thyroid hormone levels. Therefore, your medication needs may vary during pregnancy. Your doctor will likely check your blood levels of thyroid hormone every 6-8 weeks during pregnancy and four weeks after your medication dose is changed.

Prevention

There are no current guidelines to prevent thyroid disorders in pregnancy.

Revision Information

  • The American Congress of Obstetricians and Gynecologists

    http://www.acog.org

  • American Thyroid Association

    http://www.thyroid.org

  • The Society of Obstetricians and Gynaecologists of Canada

    http://www.sogc.org

  • Thyroid Foundation of Canada

    http://www.thyroid.ca

  • American College of Obstetricians and Gynecologists. Thyroid disease in pregnancy. Practice Bulletin No. 37 . August 2002 (reaffirmed 2013).

  • Graves’ disease. American Thyroid Association website. Available at: http://www.thyroid.org/patients/brochures/Graves%5Fbrochure.pdf. Published 2012. Accessed June 10, 2013.

  • Hashimoto’s disease. American Academy of Family Physicians Family Doctor website. Available at: http://familydoctor.org/familydoctor/en/diseases-conditions/hashimotos-disease.html. Updated November 2010. Accessed June 10, 2013.

  • Pregnancy and thyroid disease. National Endocrine and Metabolic Diseases Information Service website. Avialable at: http://www.endocrine.niddk.nih.gov/pubs/pregnancy. Updated March 23, 2013. Accessed June 10, 2013.

  • Torpy J, Lynm C, et al. Hyperthyroidism. JAMA . 2005;294(1):146.

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