Thyroid Disorders in Pregnancy
The thyroid is a butterfly-shaped gland located in the front of the neck. It produces hormones that control metabolism. Thyroid disorders in pregnancy can be a particular concern because pregnancy-related hormones can affect thyroid hormones. Untreated thyroid disorders in pregnancy increase the risk of pregnancy complications. It may cause harm to the developing fetus.
Hypothyroidism]]> is a disease in which the thyroid gland does not produce enough thyroid hormone.
]]>Hyperthyroidism]]> is a disease in which the thyroid gland produces too much thyroid hormone.
The Thyroid Gland
Hashimoto’s disease is the most common cause of hypothyroidism . The immune system attacks the thyroid gland. Other causes of hypothyroidism in pregnancy include the following:
- Inadequate treatment of pre-existing hypothyroidism
- Overtreatment of hyperthyroidism with antithyroid medications
- Increased estrogen levels (causes circulating thyroid hormone to become inactive)
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, such cases usually resolve spontaneously.
A risk factor is something that increases your chance of getting a disease or condition.
The following factors increase your chance of having thyroid disorders in pregnancy. If you have any of these risk factors, tell your doctor:
- Personal or family history of a thyroid disorder
- History of treatment for a thyroid disorder
- Presence of a goiter (enlarged thyroid gland)
- Hyperemesis gravidarum]]> (severe forms of morning sickness)
- Prematurely gray hair
- Family or personal history of immune problems (eg, ]]>type 1 diabetes]]> , ]]>vitiligo]]> )
If you experience any of these symptoms during pregnancy, do not assume it is due to a thyroid disorder. These symptoms may be caused by other, less serious health conditions. Many people with thyroid disorders have no symptoms at all. If you experience any one of them, see your physician.
Symptoms of Hypothyroidism
- Goiter (swelling) in the front of your neck
- A feeling of fullness or tightness in your throat
- Trouble swallowing foods or liquids
- Dry skin
- Slow heartbeat
- Weight gain
- Intolerance to cold
Symptoms of Hyperthyroidism
- Unexplained weight loss
- Heart palpitations or abnormal heart rhythm
- Protruding eyes
- Intolerance to heat
Your doctor will ask about your symptoms and medical history, and perform a physical exam. You may be referred to a doctor who specializes in hormone disorders (endocrinologist).
Tests may include the following:
- Blood tests—to measure thyroid-stimulating hormone (TSH), thyroid hormones (thyroxine, or T4, and triiodothyronine, or T3), and to look for the presence of antibodies that attack the thyroid gland
- Radioactive scan of the thyroid—to determine whether the thyroid is overactive (this is usually avoided during pregnancy, though, due to risks to the developing fetus)
Untreated hypothyroidism in pregnancy can:
- Increase the risk of miscarriage]]> and fetal death
- Negatively impact the child’s psychological development, IQ score, motor skills, attention, language, and reading abilities
To treat hypothyroidism, your doctor will prescribe an oral medication. ]]>Levothyroxine]]> (Synthroid) can replace the hormone your thyroid is not producing.
Untreated hyperthyroidism in pregnancy is associated with:
- Fetal ]]>tachycardia]]> (fast heart rate)
- Babies that are small for gestational age
- Fetal hyperthyroidism
- Congenital malformations
To decrease the risk of hypothyroidism, mild hyperthyroidism during pregnancy is often monitored closely without therapy. Antithyroid drug therapy ( ]]>methimazole]]> , ]]>propylthiouracil]]> ) is used to treat more severe hyperthyroidism. Propylthiouracil is usually chosen, since it may not pass over the placenta as much. Medicine that passes over the placenta can effect the developing fetus.
If antithyroid medications do not work, surgical removal of your thyroid gland may be performed. It is very rarely recommended during pregnancy. Treatment with radioiodine that destroys the thyroid gland, is contraindicated during pregnancy because of risk to the fetus.
Hormones associated with pregnancy can cause changes in thyroid hormone levels. Therefore, your medication needs may fluctuate widely 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.
American Association of Clinical Endocrinologists
The American College of Obstetricians and Gynecologists
American Thyroid Association
Graves’ disease. American Thyroid Association website. Available at: http://www.thyroid.org/patients/brochures/Graves_brochure.pdf . Accessed August 12, 2005.
Hashimoto’s disease: what it is and how it’s treated. American Academy of Family Physicians website. Available at: http://familydoctor.org/548.xml . Accessed August 4, 2005.
Hyperthyroidism. JAMA Patient Page . Available at: http://jama.ama-assn.org/cgi/content/full/294/1/146 . Accessed August 12, 2005.
Thyroid disease and pregnancy. American Thyroid Association website. Available at: www.thyroid.org/patients/brochures/ Thyroid_Dis_Pregnancy_broch.pdf. Accessed August 4, 2005.
Thyroid Disease in Pregnancy, American College of Obstetricians and Gynecologists, Practice Bulletin, No 37, August 2004.
Thyroid through the ages: the reproductive years (pregnancy). American Association of Clinical Endocrinologists website. Available at: http://www.aace.com/pub/tam2001/tam-senyrs.php . Accessed August 4, 2005.
Last reviewed November 2008 by ]]>Jeff Andrews, MD, FRCSC, FACOG]]>
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