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Patient Guide to the Management of Maternal Hyperthyroidism Before, During, and After Pregnancy

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Patient Information Page from The Hormone Foundation

The Hormone Foundations Patient Guide to the Management of Maternal Hyperthyroidism Before, During and After Pregnancy

Why were the guidelines written?

This patient guide is based on clinical guidelines written to help physicians who are evaluating and treating various types of thyroid dysfunction in women before, during, and after their pregnancy (postpartum). Pregnancy, even in women with no thyroid abnormalities, causes major changes in thyroid hormone levels. Because of the complex changes in thyroid function that occur during and after pregnancy, and because thyroid disease in the mother can affect the course of her pregnancy and the developing fetus, as well as the mothers health in the postpartum period, the diagnosis and management of thyroid diseases during pregnancy requires special considerations.

This guide summarizes information about the best way to diagnose and manage maternal hyperthyroidism, a condition in which the mother has too much of the thyroid hormones T3 and T4 (also called an overactive thyroid). A pregnant woman might overlook some of the symptoms of hyperthyroidism as just being part of pregnancy: for example, feeling warm, hard or fast heartbeats, nervousness, trouble sleeping, and nausea. However, hyperthyroidism during pregnancy, if left untreated, poses a risk for both mother and baby. Having too much thyroid hormone greatly increases your metabolism. Pregnant women with uncontrolled hyperthyroidism can develop high blood pressure and are at greater risk of heart problems. There is also a greater risk of miscarriage, premature birth, and having a baby with low birth weight. Furthermore, it is important for all women to know that thyroid dysfunction occurs in the first year postpartum in approximately 7% of all women, despite the fact that these women have had no known thyroid disease before pregnancy.

How were the guidelines developed?
The clinical guidelines were developed after an extensive review of the best clinical studies about thyroid dysfunction in pregnant and postpartum women and about the effects of treatment on the mother and baby. An international expert panel of The Endocrine Society examined evidence from studies that had been published in peer-reviewed medical journals (that is, the studies were carefully evaluated by the journals scientists and editors). The panels recommendations and suggestions were reviewed and approved by several committees and, finally, by the general membership of The Endocrine Society. No funding for the guidelines came from any pharmaceutical company.

Who is at higher risk of hyperthyroidism during pregnancy?
Eighty-five percent of all cases of hyperthyroidism during pregnancy is caused by Graves disease. Graves disease occurs when your immune system becomes overactive and forms antibodies (immune proteins) that attack the thyroid gland. This causes the thyroid to enlarge and make too much thyroid hormone.

Graves disease runs in families with a history of thyroid disease, is more common in women and most often begins between the ages of 2040. Because of the immune changes associated with pregnancy, some women develop new onset Graves disease during the first postpartum year. Most of the remaining cases of hyperthyroidism during pregnancy are due to an enlarged thyroid gland that contains a small rounded lump or lumps called nodules, which produce too much thyroid hormone.

What special considerations apply to the diagnosis and management of hyperthyroidism during pregnancy and postpartum?
Because of the harmful effects hyperthyroidism can have on the course of pregnancy, it is best to know whether you have this condition before becoming pregnant. Women with a family history of thyroid disease or any autoimmune disease are at increased risk for hyperthyroidism. Typical symptoms of hyperthyroidism can include:

Feeling too hot when others are comfortable
Trembling hand
Rapid heartbeat
Tiredness/fatigue
Weight loss even though you are eating normally or too much Trouble sleeping
Irritability and anxiety

A personal or family history of thyroid disease or any signs or symptoms of hyperthyroidism should alert your physician to perform blood tests to measure thyroid hormone and antibody levels. Hyperthyroidism is characterized by higher than normal levels of T4 and T3 and very low levels of thyroid stimulating hormone (TSH). TSH is a hormone made by the pituitary gland and stimulates the thyroid gland to make thyroid hormone. However, when the thyroid gland becomes overactive, there is no need for TSH and the pituitary gland stops making it. In addition to low TSH and high T4 and T3, most patients with Graves disease also have measurable TSH receptor antibodies. These antibodies can be passed across the placenta from the mother to the baby and stimulate the babys thyroid, causing fetal thyroid dysfunction and other medical problems. All newborns of mothers with Graves disease should be examined for evidence of thyroid dysfunction and treated if necessary.

Postpartum thyroiditis (PPT)a thyroid inflammation that occurs in 7% of all women during the first year postpartum. PPT has different phases, the first of which is the hyperthyroid phase. Frequently, the hyperthyroid phase of PPT clears up without treatment after a period of a few weeks or months and thyroid function returns to normal. However, in many women the hyperthyroid phase of PPT damages their thyroid gland and a hypothyroid phase of the disease follows. Women in the hypothyroid phase often have symptoms of weight gain, dry skin and tiredness and require treatment. Approximately 30% of women who have had PPT will develop permanent hypothyroidism within the next 10 years. Annual evaluation of thyroid hormone levels is, therefore, recommended.

What is the recommended treatment for hyperthyroidism?
For hyperthyroidism due to Graves disease or overactive thyroid nodules, antithyroid drug therapy should either be started (for women with newly diagnosed hyperthyroidism) or adjusted (for those with a prior diagnosis) to maintain the maternal thyroid hormone levels in the appropriate range. For pregnant and breast-feeding women, the antithyroid drug propylthiouracil (PTU) is recommended. Methimazole may be prescribed if a patient has problems with PTU.

Pregnancy has a direct impact on the activity level of Graves disease. Hyperthyroidism caused by Graves diseases typically improves throughout pregnancy. On the other hand, Graves disease frequently worsens during the first six months postpartum. Because of these changes your doctor may need to adjust your dose of antithyroid drug therapy, both during and after pregnancy.

Most cases of Graves disease during pregnancy can be treated with antithyroid medication. On occasion, and under some circumstances, surgery to remove part of the thyroid may be needed:

  • The patient has a very bad reaction to antithyroid drug therapy.
  • The patient continues to require high doses of antithyroid drug therapy over time.
  • The patient does not take her medication as prescribed and has uncontrolled hyperthyroidism.

The best time for such surgery is during the second trimester of pregnancy (months 46).

Treatment with radioactive iodine should not be given to a woman who is, or may become, pregnant because the radioactive iodine can cross the placenta and destroy the babys thyroid.

What can you do to help your treatment process? You and your doctor should be partners in your care. Before becoming pregnant, consult with your doctor about your thyroid status. It is important that you provide your doctor with a full description and history of your symptoms, however minor they may seem, as well as a thorough medical and family history. When a diagnosis of hyperthyroidism is made, discuss treatment options with your doctor. Radiation therapy should be avoided if you are pregnant or if you plan on becoming pregnant in the next 612 months. If antithyroid drug therapy is prescribed, it is important to take your medication as instructed during pregnancy and breast-feeding. Keep regular appointments with your doctor and ask questions. You should tell your doctor about any side effects you are having. Be sure to follow your health care providers advice about your nutritional needs.

Footnotes

  • This patient guide is the second of three guides based on the Endocrine Societys clinical guidelines on maternal thyroid dysfunction before, during and after pregnancy. Part 1 addresses maternal hypothyroidism and part 3 addresses thyroid nodules and thyroid cancer.

Responses to this article
Peter Laurberg

  • Thyroidectomy in pregnant women with Graves hyperthyroidism may lead to fetal hyperthyroidism The Journal of Clinical Endocrinology & Metabolism published online September 17, 2007

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