Congenital Hypothyroidism

What is congenital hypothyroidism?

Congenital hypothyroidism is a type of hypothyroidism that’s present from birth. It happens when a newborn’s thyroid gland doesn’t develop properly or work like it should, resulting in thyroid hormone deficiency.

Left untreated, congenital hypothyroidism can cause developmental delays. In fact, congenital hypothyroidism is one of the most common preventable risk factors for intellectual disability. For this reason, healthcare providers screen newborns shortly after birth to check their thyroid function. They can do this with a simple blood test. This test is mandatory in the U.S.

Congenital hypothyroidism occurs in about 1 out of every 3,000 to 4,000 newborns. Babies assigned female at birth (AFAB) are twice as likely to have the condition.

Most babies with congenital hypothyroidism will need lifelong treatment in the form of medication (thyroid hormone replacement). But some babies have temporary hypothyroidism that goes away on its own in a few weeks or months. With proper treatment, children with congenital hypothyroidism can lead very normal lives.

What are the symptoms of congenital hypothyroidism?

It’s not always obvious when a newborn has congenital hypothyroidism. That’s one reason why thyroid screening is so important.

Early warning signs can develop over the first few weeks of life and may include:

• Constipation
• Decreased muscle tone (hypotonia)
• Feeding difficulties
• Jaundice that doesn’t go away
• Lethargy
• Hoarseness when crying
• Hypothermia (low body temperature)

Without treatment, babies can develop these congenital hypothyroidism symptoms over time:

• Abdominal distension (swollen belly)
• Anemia
• Bradycardia (slow heartbeat)
• Coarse hair
• Cold, dry skin
• Goiter (enlarged thyroid gland)
• Hypotension (low blood pressure)
• Macroglossia (enlarged tongue)
• Puffiness around the eyes

What causes congenital hypothyroidism?

The most common cause of congenital hypothyroidism is a group of conditions called thyroid dysgenesis. These conditions include:

• Ectopic thyroid gland (when the thyroid gland is in a different location than it should be)
• Thyroid agenesis (missing thyroid gland)
• Thyroid hypoplasia (underdeveloped thyroid gland)

Less common causes include:

• Genetic mutations (changes) that affect thyroid hormone production
• Iodine deficiency during pregnancy
• Taking certain medications during pregnancy (like lithium or antithyroid drugs), which can interfere with thyroid hormone production
• Treatments for thyroid cancer (like radioactive iodine) during pregnancy

What are the complications of congenital hypothyroidism?

Without treatment, congenital hypothyroidism can lead to:

• Anemia
• Developmental delays
• Hearing loss
• Heart failure
• Intellectual disabilities
• Vision issues

How is congenital hypothyroidism diagnosed?

In the U.S. and many other countries, healthcare providers do routine thyroid screenings on all newborns. To do this, they’ll take a small blood sample from your baby’s heel to check their levels of:

• TSH (thyroid-stimulating hormone), which supports thyroid hormone production
• T4 (thyroxine), which helps control growth and metabolism

If your baby’s blood test results are abnormal, your provider may also take imaging tests (like a thyroid scan or ultrasound) to confirm a diagnosis or rule out other conditions.

How is congenital hypothyroidism treated?

Congenital hypothyroidism treatment usually involves taking medication to replace the missing thyroid hormone. The most common thyroid hormone is levothyroxine — a synthetic hormone that mimics your baby’s T4 hormone. It comes in tablet form, so you’ll need to crush the pill and mix it into your baby’s formula, breastmilk or water. Your child’s endocrinologist can show you how to do this and tell you whether there are any formulas you should avoid. (Some soy-based formulas can interfere with thyroid hormone absorption.)

Your baby will need to start medication within the first month of life to prevent permanent developmental delays or intellectual disabilities. A healthcare provider will check your baby’s blood thyroid hormone levels regularly to ensure they’re getting the right amount of medication. Typically, they’ll run blood tests:

• Every one to two months until your baby reaches 6 months of age
• Every two to three months after your baby reaches 6 months of age

Most people with congenital hypothyroidism need to take medication for the rest of their lives. Some may only need treatment on a temporary basis. Your child’s endocrinologist can tell you what to expect in your situation.

Can congenital hypothyroidism be prevented?

Because genetics play a role, it’s not always possible to prevent congenital hypothyroidism. But if you’re pregnant, ask your healthcare provider how to reduce your baby’s risk. They can run tests to check your iodine levels and make any necessary adjustments to your medications.

What’s the life expectancy for people with congenital hypothyroidism?

Life expectancy for people with congenital hypothyroidism is the same as for people without the condition. As long as your baby begins treatment right away, the outlook is excellent.

When your child reaches adulthood, they should be able to work in any occupation and have a family of their own if they so desire. Except for taking thyroid hormone replacement every day, your child will be able to live a perfectly typical life.

When should I see my healthcare provider?

If your baby has congenital hypothyroidism, an endocrinologist will check their thyroid hormone levels regularly. But you should still let your healthcare provider know if your child’s symptoms come back after starting medication. They may need to adjust the dosage.

What questions should I ask my doctor?

Here are some questions you may want to ask your child’s endocrinologist:

• Do you know what caused my baby’s condition?
• Is their condition temporary or permanent?
• Will they need medication for the rest of their life?
• How will you figure out the correct dosage?
• How do I give my child their medication?
• What happens if they miss a dose?
• How often will they need thyroid tests?