Breastfeeding and Hyperthyroidism

Overactive Thyroid in The Nursing Mother

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What is Hyperthyroidism?

Hyperthyroidism is a medical condition where your body's thyroid gland makes too much thyroid hormone. Symptoms of an overactive thyroid include:

  • Weight loss
  • Nervousness
  • Anxiety
  • Palpitations
  • Increased Heart Rate
  • An Enlarged Thyroid Gland
  • Insomnia
  • Difficulty Gaining Weight
  • Feeling Warm
  • Sweating

Breastfeeding and Hyperthyroidism

If you were being treated for Graves disease or a hyperthyroid condition before you became pregnant, you should continue to see your doctor for monitoring throughout your pregnancy and while you are breastfeeding.

Your thyroid levels may change as your body changes, so your doctor may need to adjust your medication during and after your pregnancy.

If you have not had any thyroid issues in the past, thyroid symptoms can begin after the birth of your baby. Some women develop mild hyperthyroidism followed by hypothyroidism in the months after the birth of their baby. This is called postpartum thyroiditis. The overactive phase of postpartum thyroiditis usually resolves itself within a few weeks and does not necessarily require any treatment. However, if the symptoms of hyperthyroidism are severe or last longer than a few months, you doctor may want to treat the symptoms by putting you on a low dose of medication and monitoring both you and your baby.

Breastfeeding with hyperthyroidism has it's challenges. In addition to the symptoms listed above, an overactive thyroid may also cause a slow or difficult let-down reflex and an overabundant supply of breast milk.

If you are experiencing the symptoms of an overactive thyroid, see your doctor for the proper diagnosis and treatment.

Diagnosing An Overactive Thyroid

Your doctor may want to do a thyroid scan to check your thyroid function. If you are breastfeeding, you do not want to use radioactive iodine for your uptake scan.

Ask your doctor to perform the scan without it, or postpone the scan until after you have weaned your child. If you do choose to use radioactive iodine for testing, do not breastfeed your child for 48 hours after taking the radioactive medication. While you are waiting to start breastfeeding again, you can pump and dump your breast milk in order to prevent engorgement and maintain your milk supply.

Other testing used to diagnose hyperthyroidism include blood tests, ultrasound, and/or needle biopsy of the thyroid. All of these tests are safe to have while you are breastfeeding.

Treatments For Hyperthyroidism

Antithyroid Medications: PTU (propylthiouracil) and Tapazole (methimazole) are antithyroid medications that are used to help your body make less thyroid hormone. They are both considered to be safe to take while you are breastfeeding. Studies show that the amount of these medications that will make it into your breast milk is very small. Therefore, the benefits that breastfeeding will provide your child far outweigh any risks that these medications may pose.

Thyroidectomy: A thyroidectomy is a surgery that removes all or part of your thyroid gland. Other than having to be away from your child during the surgery, you do not have to stop breastfeeding for this procedure.

Once the surgery is over and you feel up to it, you can begin breastfeeding again.

Radioactive Iodine Treatment: Radioactive iodine passes into breast milk in very high amounts. It is considered very dangerous for the breastfeeding infant. You can not breastfeed if you take radioactive iodine until there are no traces of the medication left in your breast milk. Depending on the dose, this could take weeks or months. Most women will fully wean when this treatment is necessary but temporary weaning may also be possible. You can try to pump and discard your milk to help maintain your supply during the time that you are unable to breastfeed.

However, you have to be sure that your breast milk is free of all radioactive medication, and safe for your child, before you begin nursing again. Talk to your doctor about your options. 

Tips For Breastfeeding with Hyperthyroidism:

  • See your doctor for regular monitoring and be sure that your doctor knows that you are breastfeeding.
  • Take your medication as ordered by your doctor and follow his instructions and treatment plan.
  • Take your thyroid medication after your breastfeed, instead of before.
  • You should not smoke while you are breastfeeding, especially if you have hyperthyroidism. Smoking can make the symptoms of hyperthyroidism even worse.
  • Stress can also increase the symptoms of an overactive thyroid. Try to reduce your stress, get enough rest and eat a healthy, well-balanced diet.
  • Wear a supportive nursing bra and use cabbage leaves or cold compresses to relieve the pain and swelling that can result from an overabundant milk supply.
  • If you are experiencing a slow let-down, use a warm compress or a breast pump to get the milk flow started before you begin breastfeeding.
  • Ask your doctor if you can take Tylenol (acetaminophen) or Motrin (ibuprofen) if you are in pain.

Tell your baby's doctor about any medications that you are taking. Medications given for hyperthyroidism can affect your baby's thyroid. If you are hyperthyroid and take medications, you can still breastfeed, but your baby needs to be monitored for signs of hypothyroidism and/or an enlarged thyroid gland.  


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Glatstein M. M., Garcia-Bournissen F., Giglio N., Finkelstein Y. and Koren G. Pharmacologic treatment of hyperthyroidism during lactation. Canadian Family Physician. 2009. 55(8): 797-798.

Kapcala, L. P. Galactorrhea and thyrotoxicosis. Archives of internal medicine. 1984. 144(12): 2349.

Lawrence, Ruth A., MD, Lawrence, Robert M., MD. Breastfeeding A Guide For The Medical Profession Sixth Edition.  Mosby. Philadelphia. 2005.

Mandel, S. J. and Cooper, D. S. The use of antithyroid drugs in pregnancy and lactation. Journal of Clinical Endocrinology & Metabolism. 2001. 86(6): 2354-2359.

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