Hypothyroidism is when the thyroid gland produces too little thyroid-stimulating hormone (TSH). In teens, this can affect growth and puberty.

Hypothyroidism (underactive thyroid) usually appears in people ages 60 or over, but it can affect children and teens. Reasons for this include Hashimoto’s thyroiditis, an autoimmune condition, and some medical treatments.

This article discusses how hypothyroidism can affect teens.

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Hypothyroidism can affect children and teens for various reasons. Genetic and environmental factors may play a role.

Congenital hypothyroidism

Congenital hypothyroidism is when there is a problem with the thyroid gland from birth.

The gland may be:

  • absent
  • too small
  • in the wrong place
  • unable to produce enough hormone for other reasons

Fewer than 5% of cases are inherited, though 15 to 20% are due to genetic factors. The others result from a lack of iodine in the birth parent’s diet during pregnancy. It is a lifelong condition unless the newborn receives treatment.

Acquired hypothyroidism

Acquired hypothyroidism is hypothyroidism that is not present at birth but appears later.

Hashimoto’s thyroiditis

Hashimoto’s thyroiditis is the most common type of acquired hypothyroidism. It is an autoimmune disorder in which the immune system mistakenly attacks healthy thyroid cells, leading to inflammation in the thyroid.

The inflammation damages the thyroid gland, which can no longer produce enough thyroid hormone. This is hypothyroidism. In turn, another gland — the pituitary gland — will prompt the thyroid to produce more of the hormone. This process can lead to an ongoing imbalance of the thyroid hormone.

Other causes

Besides Hashimoto’s thyroiditis, the possible reasons for acquired hypothyroidism in teens can include:

  • surgery to remove the thyroid gland, for example, because of thyroid nodules, Graves’ disease, or thyroid cancer
  • thyroiditis, a temporary thyroid inflammation that may stem from a viral infection
  • radiation treatment, for instance, to treat Hodgkin lymphoma
  • some medications, such as amiodarone or lithium, which can affect thyroid function
  • too much or too little iodine, which also affects how the thyroid works
  • damage to the pituitary gland, which tells the thyroid gland how much hormone to produce

How does hypothyroidism affect children?

Symptoms of an underactive thyroid can develop slowly and may not be noticeable for a long time.

In children and teens, they include:

  • slow height gain
  • delays in puberty
  • enlargement of the thyroid, resulting in a goiter or lump at the front of the throat

Other possible signs and symptoms include:

Without treatment, congenital hypothyroidism can lead to mental and physical developmental problems in childhood and the teenage years.

How does hypothyroidism affect different parts of the body?

To diagnose hypothyroidism, a doctor will likely:

  • ask about symptoms
  • ask about individual and family medical history
  • do a blood test to check levels of TSH and thyroid hormone
  • do a blood test to check for antibodies that could indicate Hashimoto’s thyroiditis

Subclinical hypothyroidism

Mild or subclinical hypothyroidism is when TSH levels are slightly high, but thyroid hormone levels are still within the expected range.

A doctor may diagnose mild hypothyroidism in a teen if TSH levels are between 4.5 and 10 milli-international units per liter (mlU/L) while levels of another hormone (FT4) are in a typical range.

What are the ranges for TSH levels, and what do they mean?

Treatment will aim to balance the levels of thyroid hormone in the body. Most people can do this by taking a daily pill of a medication called levothyroxine.

Doctors do not always treat mild hypothyroidism in children and teens, as unnecessary treatment may lead to further complications. However, the doctor will monitor the person’s thyroid levels by testing every 6 to 12 months.

The outlook will depend to some extent on the reason for hypothyroidism and the treatment.

Hypothyroidism due to a temporary infection or medication use will usually resolve when the person stops using the medication or when the infection heals.

Hashimoto’s thyroiditis and surgery

Hypothyroidism is permanent following surgery to remove the thyroid, and it is usually permanent with Hashimoto’s. However, with levothyroxine treatment and regular monitoring, a young person with hypothyroidism can expect to live as fully as their peers.

Congenital hypothyroidism

All newborns in the United States have hormone function tests at birth. Those with a problem usually do not have symptoms or future complications if they receive treatment within 2 weeks of birth.

Subclinical thyroiditis

Most cases resolve in time, although this can depend on individual factors. In some cases, overt or full hypothyroidism can develop.

Here are some questions people often ask about hypothyroidism in teens.

What are the symptoms of thyroid problems in female teens?

Symptoms specific to female teens include delayed puberty and heavy or irregular periods.

How can you tell if a child has thyroid problems?

Signs include slow growth, fatigue, hair loss, and delays in puberty. However, only a thyroid blood test can confirm hypothyroidism.

What is the average age of hypothyroidism diagnosis?

Hypothyroidism is more common in people ages over 60 years. Hashimoto’s disease can affect teens and young females but is more common in women ages 30 to 50 years.

What other conditions might occur alongside thyroid disease in children?

Hashimoto’s disease is the most common cause of acquired hypothyroidism. Other autoimmune conditions are more common in people with Hashimoto’s disease. These include celiac disease, type 1 diabetes, and lupus, among others.

Children with Down syndrome also have a higher chance of hypothyroidism.

What is the link between hypothyroidism and diabetes?

Hypothyroidism, or underactive thyroid, is when a person’s thyroid gland produces too little thyroid hormone.

It can affect teens for various reasons, but the most common is Hashimoto’s thyroiditis, an autoimmune condition in which the immune system mistakenly attacks healthy thyroid cells.

Hypothyroidism can affect growth and development in teens. Daily treatment with levothyroxine means that hypothyroidism does not need to affect a person’s quality of life or activity levels.