Congenital Hypothyroidism

Overview

Congenital hypothyroidism means a baby is born with a thyroid gland that does not make enough thyroid hormone. The thyroid is a small butterfly-shaped gland in the neck. The hormone it makes is important for growth, brain development, and keeping the body's energy use on track. When the gland cannot make enough of it, a baby's body and brain may not develop as they should — unless the missing hormone is replaced. The good news is that newborn screening finds almost all cases in the first days of life, and treatment started early lets most children grow up healthy and reach their full potential.

It is uncommon but not rare. About 1 in 2,000 to 1 in 4,000 babies are born with it, depending on the region and how screening is done. Because it is one of the conditions every newborn is checked for, doctors are very used to spotting and treating it.

It affects newborns, and it happens slightly more often in girls than in boys. It can occur in any family, and most babies with congenital hypothyroidism have no family history of it at all. Some babies have a higher chance because of certain genetic conditions or because the mother had a thyroid problem or low iodine intake during pregnancy.

Symptoms

Common symptoms

• No obvious symptoms at all in many newborns — this is very common and is the main reason screening exists
• Being very sleepy and feeding slowly or weakly
• Constipation and a swollen, hard tummy
• Yellowing of the skin and eyes (jaundice) that lasts longer than usual
• Feeling cold, with cool or mottled skin
• A hoarse cry or a quiet, weak cry
• A puffy face, swollen eyelids, or a large tongue
• A soft spot on the head (fontanelle) that feels larger than expected, or a belly button that bulges out (umbilical hernia)
• Slow weight gain or poor growth

Symptoms in children

• Slower than expected growth, or a child who stays shorter than their friends of the same age
• Delayed sitting, crawling, walking, or talking
• Tiredness, low energy, or difficulty concentrating at school
• Constipation that keeps coming back
• Dry skin, brittle hair, or hair loss
• Feeling the cold more than other children
• Puberty starting later than expected
• In a child already on treatment, these signs can mean the dose needs adjusting — let your doctor know

Symptoms in older adults

• This condition is present from birth, so it is not something that first appears in adulthood
• Adults who were diagnosed and treated as babies usually stay well with ongoing treatment and check-ups
• If treatment is stopped or the dose becomes too low, adults may notice tiredness, weight gain, constipation, dry skin, low mood, or feeling cold
• Adults with treated congenital hypothyroidism may have a slightly higher chance of high blood pressure or hearing problems, so routine health checks are worthwhile

Causes

Main causes

• The thyroid gland did not form properly, is smaller than usual, or is in the wrong place in the neck (called thyroid dysgenesis). This is the most common cause.
• The gland formed but cannot make thyroid hormone properly because of a missing or faulty enzyme (called dyshormonogenesis). This can run in families.
• Too little iodine in the mother's diet during pregnancy — iodine is the raw material the thyroid needs to make hormone
• Rarely, the problem is in the brain's signals (the pituitary or hypothalamus) that tell the thyroid to work, rather than in the thyroid itself
• Certain medicines taken during pregnancy, or antibodies from the mother's own thyroid condition, can affect the baby's thyroid for a while
• Some genetic conditions and chromosome changes are linked with an underactive thyroid

Risk factors

• A family history of thyroid problems, especially an underactive thyroid in a parent or sibling
• The mother having low iodine intake or a diet very low in iodine during pregnancy
• The mother having an autoimmune thyroid condition, or taking certain medicines during pregnancy
• Certain genetic syndromes, such as Down syndrome or Turner syndrome
• Being born prematurely or having a low birth weight — though most babies with the condition are born at a normal weight and with no risk factors at all

When to see a doctor

See a doctor urgently if:

• Your baby is very sleepy, hard to wake for feeds, or not feeding well
• Jaundice is still present after two weeks of age
• Your baby is very constipated, has a swollen tummy, or is not gaining weight
• Your baby feels unusually cold, has a hoarse cry, or seems very floppy
• You have been told a screening test result needs repeating — act on this quickly, even if your baby seems perfectly well
• Your child on treatment develops a fever, vomiting, or diarrhoea that makes it hard to keep the medicine down — ask your doctor or pharmacist what to do

Book a routine appointment if:

• You have questions about the newborn screening result or want it explained
• You notice your child growing more slowly than their friends, or falling behind on growth charts
• Your child seems tired, low in energy, or is struggling at school
• You need advice about giving the daily tablet, timing it with feeds, or what to do when routines change
• Your child is starting school or changing doctors, and you want the treatment plan shared clearly
• Before, during, and after pregnancy in later life — the dose usually needs adjusting
• You are planning another pregnancy and have a family history of thyroid problems

Diagnosis

In almost every case, the first clue comes from the newborn blood spot (heel prick) screening test, done when a baby is about five days old. If that test suggests a low thyroid level, your baby will have a blood test from a vein to confirm it. This confirmation is usually arranged within a few days, because starting treatment quickly matters. Your baby may also have a scan or picture of the thyroid gland to find out which type of problem it is. None of this means you did anything wrong — the condition develops before birth and cannot be caused by anything you did or did not do in pregnancy.

Tests that may be done

• Newborn blood spot screening (heel prick test) — a few drops of blood taken from the baby's heel, usually around day five
• A confirmatory blood test from a vein to measure thyroid hormone and thyroid-stimulating hormone (TSH) levels accurately
• An ultrasound scan of the neck to see whether the thyroid gland is there, its size, and its position
• Sometimes a small scan using a tiny amount of tracer to see how the gland is working — this is done in specialist centres
• Blood tests to check for antibodies from the mother, in some cases
• Genetic testing in certain situations, especially if the condition may run in the family
• Ongoing blood tests throughout childhood to check the dose is right, plus growth and development check-ups

What to expect at your appointment

The confirmation process usually moves quickly. You may be contacted by a specialist children's doctor (a paediatrician or paediatric endocrinologist) within days of the screening result. They will explain what the tests showed, talk you through the treatment, and show you how to give the daily tablet. Expect a lot of information at once, so it helps to bring someone with you and to write down your questions. You will usually have a follow-up appointment within a few weeks, and then regular check-ups with blood tests as your child grows. These appointments may feel frequent at first, but they become less often over time.

Treatment

Congenital hypothyroidism is treated by giving the body the thyroid hormone it cannot make on its own. This is a replacement of something the body should normally produce, a bit like topping up a vitamin. Treatment is started as soon as the diagnosis is confirmed — ideally within the first two weeks of life — and continues for life. With the right dose, a child grows and develops normally, and most families find the routine becomes second nature quickly.

Self-care at home

• Give the daily tablet at roughly the same time each day, and follow your doctor's or pharmacist's instructions about timing around feeds
• For babies, the tablet is usually crushed and mixed with a little water or breast milk and given by syringe — ask your pharmacist to show you exactly how
• Never stop or change the dose on your own, even if your child seems completely well
• Keep a simple record of doses, blood test dates, and any missed doses so you can discuss them at appointments
• Tell any doctor, nurse, or dentist your child sees that they have congenital hypothyroidism and are on treatment
• Ask about a medical alert card or letter you can carry, especially for school trips or hospital visits
• If a dose is missed, ask your doctor or pharmacist what to do rather than doubling up
• Attend growth checks, hearing tests, and developmental reviews when they are offered — they are a chance to catch small issues early

Medical treatments

The standard treatment is a daily thyroid hormone replacement medicine, taken as a small tablet. Your doctor will work out the starting dose based on your baby's weight and test results, and will adjust it regularly as your child grows — babies and young children need relatively larger doses than adults. Blood tests every few weeks in the first year, then less often, show whether the level is just right. Your doctor will aim for a level that supports normal growth and brain development without causing symptoms of too much hormone. Doses are always individual, so never use another child's medicine or an old prescription. If your child has trouble swallowing tablets, ask your pharmacist about suitable options for their age.

When is surgery considered?

Surgery is almost never needed for congenital hypothyroidism. In rare cases, a child may be born with a thyroid gland in an unusual place, such as near the tongue, and surgery might be considered later if it causes problems. Some children with related structural issues may need a small procedure, but this is decided case by case by a specialist team. For the vast majority of children, treatment is medicine only.

Living with this condition

Life with congenital hypothyroidism mostly means a small daily medicine and regular check-ups. Once you have a routine, it fits easily into normal family life. Many parents find it helpful to link the tablet to another daily habit, such as the first morning feed or brushing teeth. As your child grows, teach them about their condition in simple, positive words so they can take charge of their own medicine as a teenager. Keep your child's school informed, and let them know who to contact if there is a concern.

Lifestyle tips

• Treat your child like any other child — play, sports, school trips, and sleepovers are all fine
• Keep a simple health folder with test results, appointment letters, and the treatment plan, so any new doctor can see the whole picture quickly
• Plan repeat prescriptions ahead of holidays so you never run out
• Tell your child's teachers or carers what to do if a dose is missed or if your child becomes unwell
• Encourage a positive attitude to the medicine — it is a daily top-up, not a sign of illness
• As your child becomes a teenager, help them practise managing their own appointments and prescriptions before they move to adult services

Diet and exercise

No special diet is needed. A normal, balanced diet with enough iodine supports thyroid health — milk, dairy products, eggs, and fish are good sources. Very large amounts of certain foods, such as raw cabbage or soy in huge quantities, are not usually a problem in normal eating, but it is worth mentioning any unusual or restrictive diets to your doctor. Regular play, sport, and movement are encouraged and help growth, bone health, and mood. If your child takes iron or calcium supplements, ask your pharmacist about spacing them away from the thyroid tablet, because they can affect how well it is absorbed.

Mental health and emotional wellbeing

Being told your newborn has a lifelong condition can bring a wave of worry, guilt, or shock — these feelings are completely normal, and they usually ease as you see your child thriving. Some parents feel anxious before every blood test or growth check. Older children and teenagers may feel different from their friends or resent taking daily medicine; this is common and worth talking about openly. If low mood, anxiety, or worries about the condition are affecting you or your child, please speak to your doctor. If you or your child ever feel in crisis or unable to cope, contact your local emergency number or a local mental health crisis service straight away — you do not have to manage alone.

Prevention

Most cases of congenital hypothyroidism cannot be prevented, because the thyroid gland develops in the womb before anyone can influence it. What can be done is to make sure the condition is found early — which is exactly what newborn screening does. Ensuring enough iodine in the diet before and during pregnancy supports the baby's thyroid development; in many countries, iodine is added to table salt for this reason. If you are pregnant or planning a pregnancy and have a thyroid condition, keep your appointments and tell your doctor, as your treatment may need adjusting.

Vaccines

There is no vaccine for congenital hypothyroidism. Routine childhood vaccinations should go ahead as normal — the condition is not a reason to delay them. If your child is unwell with a fever, follow the usual advice about when to reschedule.

Screening programmes

Newborn screening is the single most important step. A few drops of blood are taken from your baby's heel, usually around five days after birth, and tested for congenital hypothyroidism and several other conditions. This test finds almost all cases, often before any symptoms appear. If you are asked to bring your baby back for a repeat test, please do so promptly — it is a quick test and it matters. Some countries also check thyroid levels in pregnant women, especially those with symptoms or a family history.

Complications

If left untreated

• Slower growth and a shorter final adult height
• Delayed development of movement, speech, and learning, which can become permanent if treatment is started late
• Hearing problems
• Ongoing constipation and feeding difficulties
• In the newborn period, a rare but serious crisis with very low body temperature, poor feeding, and breathing difficulties
• Later in life, a higher chance of high blood pressure and heart problems if the condition is poorly controlled
• Difficulties with concentration and school performance

Long-term outlook

The outlook is genuinely good. Babies diagnosed through newborn screening and treated in the first weeks of life usually grow and develop just like their peers, and most do well at school and in adult life. The key is starting treatment early and keeping up with check-ups and blood tests. Some children need a bit of extra support with learning or hearing, and these needs are picked up and helped when they are reviewed regularly. Your child can play sports, go to university, travel, and have a family — this condition is part of their life, not a limit on it.

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