Written by Ada’s Medical Knowledge Team
What is congenital hypothyroidism?
Congenital hypothyroidism is a condition that can affect newborn babies. The word congenital means present at or before birth, while hypothyroidism refers to insufficient levels of thyroid hormone. While congenital hypothyroidism is a serious condition, it can generally be detected and treated early enough to prevent complications, thanks to routine screenings after birth in many parts of the world. 1 2 3
The thyroid is a small, butterfly-shaped gland found in the lower part of the neck, just below the voice box. Hormones released by the thyroid control the body’s growth and metabolism. They affect key physical processes like heart rate, digestion, weight and temperature. 4 Adequate levels of thyroid hormone are essential for the healthy physical and mental development of a baby. 2
Congenital hypothyroidism affects approximately one in every 2000 to 4000 newborns 5 and has been found to be more common in female babies. 1 The condition occurs when the baby’s thyroid gland does not develop or function properly. In the majority of cases, the gland itself is absent, smaller than normal or located in the wrong place. However, congenital hypothyroidism may also result when the gland is normal, but there are problems with the production of thyroid hormone. 6
In the USA, UK and many other parts of the world, all newborn babies are screened for congenital hypothyroidism within a few days of birth. A simple heel-prick blood test is typically used, and if the results suggest the presence of congenital hypothyroidism, further tests will be done to confirm the diagnosis. Where necessary, treatment with synthetic thyroid hormone will be started without delay. 1 2 6 7
If left untreated, congenital hypothyroidism can lead to severe, irreversible mental impairment and poor growth. However, with prompt, proper treatment and monitoring, the prognosis is excellent, and infants with congenital hypothyroidism will usually grow up to lead normal, healthy lives. 1 2 6 8
Congenital hypothyroidism symptoms
Most newborn babies with congenital hypothyroidism show no obvious signs of the condition. 5 This may be because they receive some of their mother’s thyroid hormone before being delivered. They may also be able to produce a small amount of their own. 1 8
However, some babies affected by congenital hypothyroidism may be less active, sleep a lot and be difficult to feed. 6 9 If congenital hypothyroidism is severe, the following signs and symptoms may also be present: 1 2 5 ref9
- Weak cry
- Poor feeding
- Dry skin
- Poor muscle tone (floppiness)
- Cold hands and feet - they may also be mottled
- Prolonged jaundice, which is when the skin has a yellow color
- Puffy face
- Large tongue
- Swollen stomach
- Umbilical hernia
- Large fontanels, which are the soft spots on a baby’s head.
It is important that a newborn baby be screened for congenital hypothyroidism as early as possible in order to prevent complications.
In many countries, babies are screened sufficiently soon after birth that they will generally not have symptoms of congenital hypothyroidism. However, in rare cases, a baby with the condition may have symptoms immediately after birth. 5
In parts of the world where screening is not performed, a baby may not show symptoms of congenital hypothyroidism initially, but they will typically develop symptoms in the first few months after birth. 5 If you are concerned about any symptoms, you can do a free assessment using the Ada app.
Congenital hypothyroidism causes
The most common cause of congenital hypothyroidism is the baby’s thyroid gland not developing properly. The gland may be absent, smaller than normal or positioned in the wrong part of the neck. It is not known why this happens, but the malformation is not usually inherited – meaning that any siblings are unlikely to be born with the same thyroid condition. 2 3
- Problems metabolizing thyroid hormone; this may be inherited
- Problems with the hypothalamus or pituitary gland, two very important, connected parts of the brain that regulate a large number of bodily processes
- Iodine deficiency in the parent during pregnancy, though this is uncommon in developed countries
- High levels of thyroid antibodies 10 in the parent during pregnancy
- Antithyroid medication taken during pregnancy, in a small number of cases
Excessive iodine intake, congenital liver hemangiomas (non-cancerous growths of blood vessels) and certain gene mutations may also be factors in the development of congenital hypothyroidism. 11
Diagnosis of congenital hypothyroidism
In many countries, all newborn babies are screened for congenital hypothyroidism shortly after birth. This is done in hospital using a pinprick test that draws a small amount of blood, usually from the baby’s heel, to check their thyroid hormone levels. The baby will typically be checked for other conditions such as cystic fibrosis and sickle cell disease at the same time. 1
If the baby’s thyroid hormone levels are not within the acceptable range, a doctor will order further blood tests to confirm the diagnosis of congenital hypothyroidism. They may also request a thyroid ultrasound scan to be performed in order to assess the physical status of the thyroid gland. Treatment will be started immediately. 1 2
Congenital hypothyroidism treatment
Treatment for congenital hypothyroidism typically involves medication, monitoring and assessment of the baby’s development. 3
The standard treatment for congenital hypothyroidism is the prescription of synthetic thyroid hormone in the form of levothyroxine (L-T4). In many cases, it will be necessary to take levothyroxine for life, even into older adulthood. 2 9
Levothyroxine comes in tablets, which should be crushed and given to the baby in a small amount of water or milk every day. A doctor will advise on the dose needed, as well as what foods to avoid giving the baby before and after taking the medication. It is important not to mix the tablets with soy formula or any preparation containing concentrated iron or calcium. When the child is older, they can swallow the tablets on their own with a cup of water. The dose will need to be adjusted as the child grows up. 5 9
Prompt, proper treatment with levothyroxine can generally prevent complications from congenital hypothyroidism. The medication is generally considered safe and has no side-effects at the correct dose. If the dose is too low, symptoms of hypothyroidism may develop, while too high a dose can lead to symptoms of hyperthyroidism. 3
In many cases, a doctor will recommend working with a pediatric endocrinologist, a specialist in childhood conditions related to hormones, to help manage the baby’s congenital hypothyroidism as they grow up. 2 3 9
The baby will need to have regular medical check-ups to make sure that their thyroid hormone levels are adequate for healthy growth and development. Regular blood tests will also be required. Until the baby is one year old, tests will usually be necessary every one to three months or more frequently. Thereafter, it may be possible to reduce the frequency of blood tests. A doctor will adjust the dose of levothyroxine as needed. 3 9
A doctor will also monitor the height, weight and overall growth and development of the child. 3 They will periodically assess the child’s language and communication skills, motor ability and behavior. 1 If it seems necessary, a doctor may recommend having the child’s development formally evaluated. Should there be any delays in speech or learning, an early intervention program can often be arranged to assist the child. ref3
Prevention of congenital hypothyroidism
It is generally not possible to prevent congenital hypothyroidism. 9 However, pregnant people with a history of thyroid conditions, as well as those taking any medications or supplements, are advised to consult with medical practitioners before, during and after pregnancy in the interests of optimal health management.
Congenital hypothyroidism FAQs
Q: Will a baby with congenital hypothyroidism grow up normally?A: If a baby with congenital hypothyroidism is diagnosed and treated promptly and correctly, the outlook is excellent. The child has a good chance of leading a normal, healthy life. If diagnosis and treatment is delayed, however, serious developmental problems may occur. 1 2 3 9
In babies with severe congenital hypothyroidism, it is possible that there may be long-term neurocognitive, i.e. mental, effects. If treatment is not started promptly or the dosage or administering of levothyroxine is incorrect, the child may experience developmental delays. 3 8 9
Q: Is congenital hypothyroidism curable?A: Children who have an underactive thyroid from birth can be treated with synthetic thyroid hormone. In many cases, this medication will need to be taken for life. Some infants may experience transient hypothyroidism, which is when the condition goes away over time. However, it should never be assumed that a baby’s thyroid problem will clear up on its own. It is important to follow the treatment plan recommended by the doctor to avoid serious complications. 12 13
Q: Is levothyroxine safe for babies?A: Yes. Levothyroxine is a synthetic version of the thyroid hormone produced by healthy thyroid glands. It is very effective and is considered safe to take every day for babies, children and adults with hypothyroidism. However, it is important to check the baby’s thyroid levels regularly and adjust the dose of levothyroxine as needed. This is because too much levothyroxine can cause [symptoms of hyperthyroidism](symptoms of hyperthyroidism, while too little can lead to symptoms of hypothyroidism. 9
If you are concerned about any symptoms, you can do a free assessment using the Ada app.
Q: Does congenital hypothyroidism run in families?A: In a small number of cases, congenital hypothyroidism is caused by an inherited condition. In these instances, the thyroid gland itself typically appears to be healthy, but there is a problem with the production of thyroid hormone. If a doctor suspects a hereditary condition, they may refer the baby and parents to a specialist in genetics to confirm the diagnosis and advise on future family planning. 3
Q: Is congenital hypothyroidism an autoimmune disease?A: There are a number of possible causes of congenital hypothyroidism. One less common cause is the presence of thyroid antibodies 10 in the mother during pregnancy, which may be associated with an autoimmune thyroid condition. However, this does not mean that congenital hypothyroidism is an autoimmune condition.
Q: Is congenital hypothyroidism rare?A: Congenital hypothyroidism occurs in an estimated one in every 2000 to 4000 newborn babies. 5
Other names for congenital hypothyroidism
Congenital hypothyroidism is sometimes also known as:
- CH or CHT
- Underactive thyroid since birth
- Nongoitrous congenital hypothyroidism
- Thyroid hormone deficiency present at birth
- Inborn hypothyroidism
- Cretinism (outdated, pejorative)
- Congenital myxedema.