Neonatal Hyperthyroidism and Hyperthyroidism

A Risk With Graves' Disease

If you have had Graves' disease prior to or during pregnancy, your baby is at risk of being either hyperthyroid or hypothyroid at birth, conditions known as neonatal hyperthyroidism and neonatal hyperthyroidism.

Fetal and Neonatal Hyperthyroidism

If you are newly diagnosed with Graves' disease during pregnancy, you should almost always be treated with antithyroid drugs to help protect your health and that of your unborn baby.

Even if you have already been treated for Graves' disease (via RAI or surgery), or have been in remission, you can still have antibodies in your bloodstream. It's common for these antibodies to elevate during your third trimester, which can trigger hyperthyroidism in your baby.

In some babies, signs and symptoms are there from birth. In this case, your baby will be diagnosed, and sent home with you with treatment for the hyperthyroidism.

But if you were taking antithyroid drugs during your pregnancy, it can be a few days to a few weeks before the baby shows signs of hyperthyroidism. This is because the antithyroid drug you were taking passed through to the baby, but then slowly wears off after birth.

Signs and Symptoms of Hyperthyroidism in a Newborn

Some of the key signs and symptoms of hyperthyroidism in a newborn include the following:

  • An unusually small head circumference
  • An unusually prominent forehead
  • A dangerous accumulation of fluid (known as fetal hydrops)
  • Enlarged liver and/or spleen
  • Low birth weight
  • Premature birth
  • Warm, moist skin
  • High blood pressure
  • Fast heartbeat
  • Irregular heart rhythms
  • Irritability, hyperactivity, restlessness, poor sleep
  • An enlarged thyroid (goiter)
  • Difficulty breathing due to goiter pressing on the windpipe
  • Excessive or normal appetite, with poor weight gain
  • Bulging eyes, stare
  • Vomiting
  • Diarrhea

If you see these symptoms in your baby, have the baby seen immediately by a pediatrician or pediatric endocrinologist.

Fetal and Neonatal Hypothyroidism

If you are being treated with antithyroid drugs during pregnancy, your baby is at a slight risk of developing fetal or neonatal hypothyroidism. 

There are two key risk factors that can increase the risk:  

  • poor control of your hyperthyroidism throughout your pregnancy, which can cause transient hypothyroidism in your baby
  • taking high doses of antithyroid drugs, which can cause hypothyroidism in your baby

If your specialist confirms fetal hypothyroidism as a complication of your treatment, they will likely reduce your dosage of antithyroid medications. 

Note: this is different than Congenital Hypothyroidism, which is more often a permanent type of hypothyroidism due to a missing or malformed gland. 

Signs and Symptoms of Hypothyroidism in a Newborn

As part of the post-birth "heel stick test," babies born in the U.S. are automatically tested for hypothyroidism at birth. However, always make sure that this test has been done. Be sure to consult your pediatrician or pediatric endocrinologist immediately if your newborn shows any of the following symptoms of neonatal hypothyroidism:

  • A dull expression
  • Puffiness in the face
  • A thickened tongue
  • A tongue that sticks out of their mouth 
  • Episodes of choking
  • Constipation
  • Jaundice
  • Poor feeding
  • Excessive sleepiness or lethargy 
  • Lack of muscle tone 
  • Unusually short height
  • Decreased muscle tone
  • Failure to grow
  • A hoarse cry
  • Large soft spots on the skull