Levothyroxine and breastfeeding: what you need to know

Even if mom’s thyroid levels are not controlled by medication (or are in the process of being controlled) it is safe for mom to breastfeed her baby. The most common forms of thyroidism are hyperthyroidism, hypothyroidism, and postpartum thyroid dysfunction. synthroid pictures The predicted exposure level for your baby is 0.6 nanograms per kilogram per day, which is essentially undetectable. It won’t influence tests for neonatal hypothyroidism (an underactive thyroid in babies). I also urge you to nurse right before the surgery and as soon afterwards as you feel you can.

Pharmacokinetics of ATD

Recent reviews on the general use of ATD in lactation consider both ATD drugs compatible for the treatment of hyperthyroidism during lactation 29,30. It is currently recommended that breastfeeding infants of mothers taking ATD should be screened using thyroid function tests. According to the Task Force, PTU at doses of up to 300 mg/day is a second-line agent due to concerns about its severe hepatotoxicity. Pregnant women who are euthyroid, but have positive TPOAbs, may develop hypothyroidism prior to delivery. To ensure timely treatment, the task force recommends TSH testing at the time pregnancy is confirmed and every four weeks until mid-pregnancy, when thyroid function tends to stabilize.

• Hyperthyroidism in newborns is often caused by TRAb from the mother crossing the placenta during pregnancy.
• Variations that occur due to race, ethnicity, iodine intake, the presence or absence of thyroid antibodies, and even body mass index can make development of these ranges challenging.
• A small percentage of pregnant women experience postpartum thyroiditis, which is a condition when your thyroid gland becomes inflamed after you have a baby.
• Fetal ultrasound can be used to identify signs of potential hyperthyroidism.

Symptoms are initially controlled by anti-thyroid drugs (carbimazole or propylthiouracil) and beta blockers. In some cases, the gland is removed surgically or by the use of radioactive iodine and levels replaced by synthetic levothyroxine. A mother with an under active thyroid needs to take medication to return her blood levels to “normal”. It is worth repeating blood levels after delivery as anecdotally, fluctuations seem common at this time.

Is it safe for a mom to breastfeed with hypothyroidism?

For nursing moms, there are usually other diagnostic procedures that can be done instead of a scan, for example, blood tests, ultrasound, and/or fine needle biopsy. The second time I needed diagnostic procedures, my doctor skipped the scan and just did a fine needle biopsy. One thing I was worried about with thyroid surgery was the scar… in my case, it was pretty difficult to see after about 6 months (my surgeon said to give it a year), and now (4 years later) I cannot find the scar at all. Following are various diagnostic tests and treatments that moms with thyroid problems might encounter.

Thyroid medications

Fatal outcome was observed in PTU-treated children in the vast majority of cases 24,25. There is evidence that breastfeeding can help to prevent thyroid problems in both mom and baby. I-123 has a half-life of 13.2 hours, and is available in several forms. For one of the forms of the isotope, Hale suggests suspending breastfeeding for hours, depending upon the dose, but a couple of other forms/dosages do not require suspension of breastfeeding.

Hypothyroidism is most commonly caused by Hashimoto’s Thyroiditis, an autoimmune thyroid disease in which the immune system attacks and destroys the thyroid gland, resulting in underproduction of thyroid hormone. Another common autoimmune thyroid disease is Grave’s Disease, which is a leading cause of hyperthyroidism; in this disease the antibodies attacking the thyroid gland cause growth of the gland and overproduction of thyroid hormone. Some mothers may be worried that these antibodies may pass into breastmilk and harm baby, however this is not a concern.

Studies during breastfeeding have found no adverse reactions in breastfed infants clearly attributable to propranolol (Lactmed). Fetal surveillance – as well as consultation with a maternal- fetal medicine specialist – is recommended for women with uncontrolled hyperthyroidism during the second half of pregnancy and for women whose TRAb levels are three times the upper cutoff limit. Fetal ultrasound can be used to identify signs of potential hyperthyroidism. More rarely, if the fetus has a goiter, umbilical cord sampling might be recommended if it is unclear whether the fetus is hyperthyroid or hypothyroid.

As a breastfeeding mother, the idea of taking thyroid medications while breastfeeding can make you uncomfortable. Mom can resume breastfeeding as soon after the surgery as she feels up to holding baby. Gestational transient thyrotoxicosis often resolves itself after the first half of pregnancy, although management of dehydration is needed, and hospitalization may be required. Beta blockers may be considered for relief of symptoms, but ATD are not needed.

Pregnancy and fertility in thyroid disorders

The pharmakokinetic properties of all ATD have been extensively evaluated in previous studies. The half-life of MMI is 4–6 h, while PTU has a half-life of about 75 min 8. MMI has a minimal plasma protein binding, longer plasma half-life and is more lipid soluble compared to PTU. These characteristics favor the increased passage of MMI over PTU into the human milk. Moreover, PTU is more easily ionized in serum than in human milk, a phenomenon which inhibits its transfer into human milk 9. Low levels of propranolol are secreted into breastmilk, so amounts ingested by the infant are small and would not be expected to cause any adverse effects in breastfed infants.

No responsibility can be taken by the author or the Breastfeeding Network for the way in which the information is used. Clinical decisions remain the responsibility of medical and breastfeeding practitioners. The data presented here is intended to provide some immediate information but cannot replace input from professionals.