Graves' disease and breastfeeding

Graves’ disease is an autoimmune disease that affects the thyroid gland, causing it to secrete more thyroid hormones than the body needs. Graves’ disease is the most common form of hyperthyroidism and usually occurs in women between the ages of 20–40 years. High levels of thyroid hormones can cause symptoms such as weight loss, rapid heart rate, tiredness, and anxiety. 

There’s no way to stop the immune system from producing the antibodies that cause Graves’ disease. However, you can control the symptoms of Graves’ disease by decreasing the production of thyroid hormones or blocking their action. Treatments include anti-thyroid medication, radioactive iodine, or surgery (removal of the thyroid gland). Fortunately, Graves’ disease is seldom life-threatening and most women respond well to treatment. 

Radioactive iodine (RAI) readily transfers into human milk and can harm breastfeeding babies. It is one of the few drugs that must be used with caution in breastfeeding mothers. Assuming that you and your doctor agree that RAI is the best treatment for your disease, once treatment begins, you will need to suspend breastfeeding until the level of RAI is low enough to be considered safe. 

You will need to find out how long it will take the RAI to clear your body before you decide whether to wean your baby or to pump and discard your breast milk until it's safe to resume breastfeeding. Once you know the clearance time, then you can decide whether you’re willing to maintain your milk supply for 30, 60, 90, or more days until breastfeeding can be safely resumed. How long it takes the RAI to clear the body depends on a number of factors including the amount of RAI given, the type of RAI used, and how much breast milk the baby consumes daily.

Some factors to consider: 

  • RAI Dosage. If the intent of the treatment is to destroy parts of the thyroid gland, larger doses are typically used and mothers may be told to stop breastfeeding for 100 days or more. Smaller doses take less time to clear the body, so mothers receiving small doses of RAI can resume breastfeeding sooner.
  • Type of RAI. Some types of RAI clear the body within hours, while others are present for weeks or months.
  • Breast milk intake. The more breast milk a baby consumes, the greater the risk of exposure. Toddlers who are eating a variety of foods get less exposure than babies who are exclusively breastfed, but no safe level has been established. 

RAI concentrates in the thyroid gland and releases a small amount of radiation. Brief contact (1–2 hours or less) is thought to be safe, but prolonged contact (more than two hours) should be avoided until radiation levels fall. This typically takes 2–7 days but could be longer depending on the drug and the dose. Because children are more sensitive to RAI, care should be taken to minimize their exposure through close physical contact or contact with body fluids. 

For more information, talk with the radiologist who will be administering the RAI as well as your or your baby’s health care provider.

Last updated May 20, 2020

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