Congenital Hypothyroidism: Causes and Symptoms

What is Congenital Hypothyroidism?

Congenital hypothyroidism is a condition in which the thyroid gland cannot make the right amounts of thyroid hormone at birth or even before birth. Congenital hypothyroidism is fairly common, affecting 1 out of every 1,500 to 2,000 babies. It is among the most common preventable causes of intellectual disability.

What is the thyroid gland?

The thyroid gland is a butterfly-shaped gland located in the front of the neck. It makes the thyroid hormones thyroxine (T4) and triiodothyronine (T3).

The thyroid hormones are essential for:

• Normal body growth
• Brain development
• Maintaining the body’s temperature
• Regulating the body’s metabolism

What is the pituitary gland?

The pituitary gland is a pea-sized gland in the brain that makes thyroid stimulating hormone (TSH). TSH regulates the release of thyroid hormones from the thyroid.

What Causes Congenital Hypothyroidism?

In congenital hypothyroidism, a baby’s thyroid makes too little of the hormones T4 and T3. This causes the pituitary gland to increase its production of TSH to push the thyroid to work harder.

The most common causes of congenital hypothyroidism are:

• A baby’s thyroid is not in its normal location
• A baby’s thyroid hasn’t developed properly
• A baby’s thyroid hasn’t developed at all

Most of the time, we do not know why this happens.

Sometimes babies have congenital hypothyroidism because there is a problem in the production of thyroid hormones. This is often an inherited condition, which means the condition was passed down from the parents.

Sometimes, babies develop congenital hypothyroidism because the pituitary is not making enough TSH or because the thyroid gland cannot respond to TSH.

What are the symptoms of congenital hypothyroidism?

Babies with congenital hypothyroidism typically look normal and do not show symptoms. This is because the birthing parent’s thyroid hormones help the baby before birth and because the newborn screening program is able to diagnose hypothyroidism within days of birth.

Some symptoms you might notice if treatment is delayed or if the dose of thyroid hormone being given to your baby is too low include:

• Jaundice (yellowing of the skin) in a newborn for longer than usual
• Puffy face or swollen tongue
• Hoarse (raspy) cry
• Not eating well
• Cold arms and legs
• Low muscle tone
• Umbilical hernia (the belly button sticks out more than usual)
• Constipation (having trouble passing stool or having hard stools)
• Sleeping more than usual
• Poor growth

Rev. 2/2023. Mass General for Children and Massachusetts General Hospital do not endorse any of the brands listed on this handout. This handout is intended to provide health information so that you can be better informed. It is not a substitute for medical advice and should not be used to treatment of any medical conditions.