Guide to Hyperthyroidism During Pregnancy
How Does Hyperthyroidism Affect Mom and Baby?
If hyperthyroidism occurs during pregnancy and goes uncontrolled, it may lead to congestive heart failure, miscarriage, low birth weight, premature birth, preeclampsia and thyroid storm. A thyroid storm is characterized by the patient's symptoms worsening severely and suddenly.
If mom has been treated for Graves' disease in the past or has it currently, the thyroid-stimulating antibodies may make their way to the baby's bloodstream, via crossing the placenta, and stimulate the fetal thyroid. If mom is taking any anti-thyroid medications, there is a lesser risk of baby developing hyperthyroidism because these medications cross the placenta. If mom was treated with radioactive iodine or surgery, she may still have antibodies present in her blood, even though all or part of her thyroid is destroyed, even though she has normal thyroid levels. If you received any of these Graves' disease treatments, it is very important that you talk to your doctor so that he or she can keep a close eye on your baby for thyroid-related problems during your pregnancy.
A newborn with hyperthyroidism can experience rapid heart rate and this can result in heart failure. Other issues newborns face include irritability, breathing problems associated with an enlarged thyroid and poor weight gain.
Diagnosing Hyperthyroidism During Pregnancy
Carefully reviewing your symptoms and performing a few blood tests to measure the levels of T4, T3 and TSH will usually make the diagnosis. Some common hyperthyroidism symptoms are also common to pregnancy, such as being intolerant to heat, fatigue and increased heart rate. Other symptoms will help guide your doctor to a diagnosis, such as irregular and rapid heartbeat, unexplained weight loss, a fine tremor or failing to gain normal pregnancy-related weight. If hyperemesis gravidarum is the cause, you will have the associated severe nausea and vomiting.
If your symptoms are indicative of hyperthyroidism, your doctor will likely perform an ultra-sensitive TSH test. If TSH levels are below normal, it generally indicates hyperthyroidism, though low TSH levels can also be a normal part of pregnancy during the first trimester. If a blood test reveals low TSH levels, your health care provider will order another blood test to measure your T4 and T3 levels.
Diagnosis is confirmed when a blood test reveals elevated levels of free T4. If you have Graves' disease or radioactive iodine treatment or had surgery for the disease, your doctor may also test your blood to look for thyroid-stimulating antibodies.
Treating Hyperthyroidism During Pregnancy
If hyperthyroidism is mild where TSH is low but free T4 is normal, treatment is typically not required. If this condition is more severe, treatment may be done with propylthiouracil, or in some cases methimazole, two drugs that work by interfering with the production of thyroid hormone. Antithyroid drugs also can reduce the production of fetal thyroid hormone because they cross the placenta in small amounts, so it is important to prescribe the absolute smallest dose possible to prevent causing hypothyroidism in the baby.
In rare cases, surgery may be performed to remove a part or all of your thyroid gland if you cannot tolerate methimazole or proplythiouracil. Pregnant women cannot be treated with radioactive iodine because it can cause fetal thyroid gland damage.
Related Articles
Common Physical Changes Women May Experience During Pregnancy
Guide to Hypothyroidism During Pregnancy
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Resources
National Endocrine and Metabolic Diseases Information Service: Pregnancy and Thyroid Disease
Published by R. Elizabeth C. Kitchen - Featured Contributor in Health & Wellness
Rose is a freelance medical writer with a background in health care. She has been a freelance medical writer for five years. Rose is also an editor and writes on a variety of other subjects, such as sports... View profile
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