Breastfeeding and Thyroid Disease

Can a New Mother Breastfeed While Hypothyroid or Hyperthyroid?

Mother breastfeeding baby girl in bedroom
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Thyroid disease is very common, and therefore many women wonder if they will be able to breastfeed with either hypothyroidism or hyperthyroidism. Which of the medications used to treat thyroid disorders are safe when breastfeeding? What issues might you face with breastfeeding due to your thyroid condition?

Breastfeeding and Thyroid Conditions

Congratulations on having a new baby! As a new mother, you may want your new baby to have the many proven benefits of breast milk. But breastfeeding mothers are also told to be careful about taking drugs and medications, as well as receiving certain medical treatments while nursing.

Let's take a look at how either hypothyroidism or hyperthyroidism may affect breastfeeding, as well as the effects that childbirth, in general, may have on your thyroid.

How Childbirth and Breastfeeding May Affect Your Thyroid

Through pregnancy and especially around the time of childbirth, your body goes through major hormonal shifts. These hormonal changes include changes in thyroid function, and these changes may occur even if you've been stable on hypothyroid medications for a long time. In addition to thyroid conditions which are present before you give birth, many women develop thyroid problems in the months following childbirth.

Postpartum Thyroiditis

Postpartum thyroiditis is a relatively common condition which occurs in roughly 7 percent of women who have given birth. It's thought to be an autoimmune condition and may occur anytime in the first year after childbirth. A decrease in milk supply is one of the common symptoms of the condition (see below).

The most common manifestation of thyroiditis is mild hypothyroidism. On the other end of the spectrum, some women experience hyperthyroidism (often followed by hypothyroidism later on). The symptoms of postpartum thyroiditis, such as fatigue, hair loss, and mood swings, can be easily missed as these symptoms are extremely common in the postpartum period.

Most of the time no treatment is needed, though many women who have thyroiditis will develop hypothyroidism down the line. If you have thyroid autoantibodies as with Grave's disease or Hashimoto's thyroiditis, this is not a problem with breastfeeding as the antibodies are too large to be passed into breast milk.

How Thyroid Disease May Affect Breastfeeding 

If you have thyroid disease that is well controlled on medications, there is usually little problem with breastfeeding. With inadequate treatment, however, thyroid disease can affect your ability to breastfeed in a few ways. Keep in mind that even if you have been on the same dose of thyroid medication for many years, your dose may need to be changed in the postpartum period.

Hypothyroidism (either untreated or inadequately treated) can reduce your supply of breast milk. It can also contribute to a difficult let-down reflex. With optimal treatment of hypothyroidism, however, these issues should be resolved.

Thyroid function is also related to your prolactin levels, as prolactin is the hormone that helps you produce milk.

Breastfeeding in Women With Hypothyroidism (Underactive Thyroid)

In general, there is no reason why a woman who is hypothyroid and on thyroid hormone replacement therapy should be unable to breastfeed. In fact, it's essential to continue your thyroid medications while nursing.

If you are a new mother with preexisting hypothyroidism, you should have a thyroid evaluation within a few weeks of delivery at the latest. This checkup will look for changes in your thyroid function that may warrant a change in your medication dosage. It's worth repeating again that dosage changes are often required after delivery, even if you've been on the same dose for years.

While people are usually cautioned to avoid medications while breastfeeding, it's actually crucial that you continue your thyroid medications. It might help to remind yourself that you are taking thyroid hormone replacement therapy, with an emphasis on the word replacement. You are not adding a new medication to your system, but simply replacing a hormone that your body would ordinarily produce. There is little risk as long as you take your medication as directed. (You can learn more about taking  thyroid medications while breastfeeding). 

When to Talk to Your Doctor

If you are hypothyroid, and your nursing baby is losing weight, slow to gain weight, or isn't having the requisite number of bowel movements and wet diapers, you should request a thorough thyroid evaluation right away, and talk to your pediatrician about options to ensure that your baby is getting enough nutrition. There are several signs you can watch for to make sure your baby is getting enough breast milk.

While hypothyroidism can result in a decreased milk supply, there are many other possible reasons for this as well. If you are concerned about making enough breast milk check out some of the factors that can decrease your milk supply

If you are having problems with low milk supply, consider hiring a lactation consultant, or your pediatrician, for advice on medications and natural remedies that may help improve your milk supply. 

Breastfeeding in Women With Hyperthyroidism (Overactive Thyroid)

Many women with hyperthyroidism can safely breastfeed as well. If hyperthyroidism is due to postpartum thyroiditis, treatment is not usually needed.

If you have Grave's disease or had hyperthyroidism prior to pregnancy, it's important to talk to your doctor about the safety of taking antithyroid drugs while breastfeeding. Using these drugs does not automatically mean you will be unable to breastfeed, and current thought is that women should be encouraged to breastfeed despite treatment. Some medications, such as Tapazide (methimazole), however, are preferred over PTU (propylthiouracil). That said, for women who must take PTU due to an allergy to Tapazide or severe hyperthyroidism, breastfeeding may still be possible. It's important you talk to your doctor about the most recent research on this issue.

Radioactive iodine, either as part of a thyroid scan or as a treatment for hyperthyroidism (radioactive iodine ablation) should not be combined with breastfeeding as the radioactive iodine can accumulate and remain in breast milk for several weeks. If this has been recommended, you may wish to talk to your doctor about alternatives to a thyroid scan (such as a needle biopsy or other blood tests) or alternatives to radioactive iodine (such as antithyroid medications). If technetium is used for a thyroid scan, breastfeeding should be withheld for at least 30 hours following the procedure (breast milk should be pumped and tossed during this time).

Thyroid Cancer

If you have or have had thyroid cancer, it's important to talk to your doctor about any concerns relating to breastfeeding. Whether you will be able to nurse your baby depends on many factors. On a positive note, however, is that breastfeeding appears to have an inverse relationship with the development of thyroid cancer, with longer periods of breastfeeding associated with even less risk.

Bottom Line on Breastfeeding With Thyroid Disease

Thyroid disease is very common, and it's reassuring that many people will be able to take their medications and breastfeed without any problems. Changes in thyroid replacement needs are very common postpartum, and difficulty with breastfeeding may alert you to a need to have your thyroid checked. For women who have thyroid problems prior to pregnancy, it's a good idea to schedule a thorough thyroid check-up shortly after giving birth.

An inadequate amount of thyroid hormone can result in problems with milk production, your let-down reflex, and can cause symptoms which are discouraging to boot. It's common for women to become frustrated with nursing even without a history of thyroid disease, and hiring a lactation consultant can be invaluable. Often times it takes only a little guidance to help you successfully breastfeed as long as you should wish.

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