In hypothyroidism, the thyroid gland is underactive and does not produce enough thyroid hormone. Thyroid hormone controls how the body uses energy and is essential for children’s growth and development.

The thyroid is a butterfly-shaped gland at the lower front of a person’s neck. According to a 2022 study, it produces the hormones thyroxine (T4) and triiodothyronine (T3). Thyroid hormone is essential throughout life and controls a person’s metabolism, growth, and brain development.

Hypothyroidism in children can be congenital, meaning it is present at birth. Some children develop autoimmune thyroid disease, which can affect them through adolescence.

This article explains the different types of hypothyroidism that affect children and how doctors treat them.

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Hypothyroidism is when the thyroid gland does not produce enough thyroid hormone. Thyroid hormone is vital for controlling growth and other bodily functions.

Thyroid hormone affects almost every organ in a person’s body. During childhood, thyroid hormone works with growth hormones to stimulate bone growth and is essential for healthy brain development.

It also affects breathing, heart rate, and digestion. Too little thyroid hormone slows these processes and can make people feel tired, cold, and generally sluggish.

Learn more about hypothyroidism here.

The American Thyroid Association (ATA) explains that the symptoms of hypothyroidism in children can be vague and variable. They can include:

Learn more about signs and symptoms of hypothyroidism here.

Some children are born with hypothyroidism, while others may develop it later. Congenital hypothyroidism describes people born with the condition, while acquired hypothyroidism describes those who develop it later.

Congenital hypothyroidism

The ATA explains that there are different types of congenital hypothyroidism. Sometimes, babies are born without a thyroid gland, or it may not develop properly during gestation.

If the baby’s mother has hypothyroidism, thyroid-blocking antibodies may pass through the placenta during pregnancy. This form of congenital hypothyroidism is usually temporary, and the baby may only need thyroid hormone treatment for a few months.

According to research from 2017, other causes of congenital hypothyroidism are:

  • prematurity
  • iodine deficiency
  • maternal thyrotropin receptor-blocking antibodies
  • maternal or newborn iodine exposure
  • hepatic hemangioma, which is a benign tumor in the liver
  • gene mutations that change the way genes function

Congenital hypothyroidism may be more easily detected in screening programs with lower thyroid stimulating hormone (TSH) level thresholds.

Acquired hypothyroidism

Some children develop hypothyroidism after infancy. If the child’s immune system malfunctions, it can lead to an autoimmune disease where the immune system attacks healthy cells. Hashimoto’s thyroiditis is the most common autoimmune disease that causes hypothyroidism.

Learn about Hashimoto’s thyroiditis here.

According to the National Institute of Diabetes and Digestive and Kidney Diseases (NIDDKD), hypothyroidism tends to run in families. It is also more common in females.

Children who have had thyroid surgery, or radioactive iodine to treat a thyroid condition, may develop hypothyroidism, but no one knows exactly what causes autoimmune conditions.

Infections can also inflame the thyroid. Doctors call this thyroiditis, and it is usually temporary.

Learn more about autoimmune diseases here.

Hypothyroidism can interfere with children’s intellectual development, so all newborns in the United States are tested at birth, according to the NIDDKD.

For older children, doctors will perform a physical exam and find out about any family history of hypothyroidism. They may also take blood tests to check the levels of T3 and T4 in the child’s blood.

Doctors also test the levels of TSH in the blood. The pituitary gland secretes TSH to encourage the thyroid to produce T3 and T4. High levels of TSH in the blood indicate that the thyroid is not producing enough thyroid hormone to keep the body functioning properly.

If doctors suspect an autoimmune condition, they may recommend thyroid antibody tests. People produce thyroid antibodies when their immune system attacks their thyroid.

Doctors may also recommend imaging tests, such as an ultrasound, to check the size and shape of the child’s thyroid.

Learn more about the TSH test here.

Doctors usually prescribe hormone replacement medication for children with hypothyroidism. The ATA says taking levothyroxine tablets daily is usually enough to bring thyroid hormone levels back to normal.

Children with hypothyroidism need regular blood tests to check their hormone levels. Doctors will usually test the child’s blood 4–8 weeks after prescribing levothyroxine and then every 3–12 months until they are fully grown. They may ask for more tests if they change the levothyroxine prescription to a higher or lower dose.

Learn more about levothyroxine here.

The symptoms of hypothyroidism can be vague and may develop slowly. The ATA says that the most important symptoms to look out for in children and adolescents are a slowing in their growth rate and a delay in puberty.

If a child’s dose of levothyroxine is too high, they may develop hyperthyroidism symptoms. These include a rapid heart rate, excessive sweating, diarrhea, and anxiety. If caregivers notice these symptoms, they can talk with a doctor, who can arrange blood tests to check the dosage.

Some children with congenital hypothyroidism may only need short-term treatment. However, those with hypothyroidism due to Hashimoto’s thyroiditis or underdeveloped or missing thyroid glands will need lifelong treatment.

Children with Hashimoto’s thyroiditis, or other autoimmune diseases affecting the thyroid, may be sensitive to iodine, according to the NIDDKD. They may need to avoid foods rich in iodine, such as kelp, and other seaweeds.

Hypothyroidism is the result of an underactive thyroid. It can cause growth and developmental issues for children.

Most people with hypothyroidism need lifelong hormone replacement treatment to maintain healthy levels of thyroid hormones in the blood. Doctors usually prescribe levothyroxine tablets to take every day.