The thyroid gland is a butterfly-shaped gland located in the front of the neck. It produces several hormones that affect a child’s growth and development. If a child’s thyroid gland is unable to produce enough hormone to sustain their growth, the condition can be treated with hormone replacement.
In the United States, it’s estimated that hypothyroidism is present in one in 2,000 to 4,000 live births. Diagnosing and beginning treatment for hypothyroidism in the first 30 days of life is associated with better outcomes and a lower risk of permanent cognitive impairment.
Types of Hypothyroidism in Children
There are several types of hypothyroidism in children, and each type has its own unique cause and treatment plan:
Congenital hypothyroidism occurs when a child’s thyroid does not fully develop or function properly before they are born. Most cases of congenital hypothyroidism are caught during routine newborn screening lab tests. Autoimmune hypothyroidism happens when a child has a normal thyroid gland but their immune system attacks it, resulting in decreased function of the gland. This condition is usually caused by chronic lymphocytic thyroiditis (CLT) and is often referred to as Hashimoto’s thyroiditis. This condition affects about 1% to 2% of people in the United States. Acquired hypothyroidism is when a child’s thyroid gland is damaged or removed for medical reasons, such as thyroid cancer. This is rare but can happen at any age. Central hypothyroidism happens when your child has a healthy thyroid gland, but their brain does not make enough thyroid-stimulating hormone (TSH). This hormone tells the thyroid gland to work, so without it, the gland does not function properly. Central hypothyroidism is usually caused by damage to or malformation of a child’s pituitary gland or hypothalamus. It can be present at birth or acquired later on in life.
Causes
Hypothyroidism in children can be caused by several factors, including genetics, cancer treatment, nutritional deficiencies, and more.
Genetics
Most cases of hypothyroidism in children are not caused by genetic mutations, but it is possible. Congenital hypothyroidism can occur if there are mutations in genes for factors that are important to thyroid gland development or in receptors and factors along the thyroid hormone pathway. Studies have found that having a sibling with hypothyroidism, being a twin, or being conceived with the help of in vitro fertilization (IVF) are all risk factors of hypothyroidism in children. Infants born prematurely may be at higher risk for central hypothyroidism because their pituitary gland or hypothalamus may not be completely formed at birth.
If a pregnant mother has autoimmune hypothyroidism, it is possible for her to pass it on to her baby. In the case of autoimmune hypothyroidism, the immune system creates antibodies to attack the thyroid gland, resulting in decreased function. It’s estimated that 2% of cases of hypothyroidism in children are caused by a mother’s antithyroid antibodies passing through the placenta to the child.
Cancer Treatment
If your child has a history of cancer, their growth may be affected by both the disease and the treatment. Hypothyroidism in children is associated with radiation therapy, especially when the thyroid or pituitary glands are targets of the radiation.
Studies estimated that about 26.5% of children who have undergone ionizing radiation following a bone marrow transplant experience hypothyroidism. Fortunately, this type of hypothyroidism is likely to resolve on its own over a few years.
When the radiation therapy is administered to the head or neck, up to 65% of children treated are expected to experience hypothyroidism in the following five years. This is most likely to occur in children with a history of Hodgkin lymphoma or cancers of the central nervous system.
Treatment for other chronic conditions may also affect thyroid function and require close monitoring, including:
Interferon for Hepatitis C Antiepileptic drugs for seizure management
Nutritional Deficiencies
Experiencing hypothyroidism due to a nutritional deficiency is rare in the United States, but it does happen. Iodine is an essential element for our bodies and significantly affects the thyroid gland. Taking in too little or too much iodine can affect thyroid function. Our bodies take in iodine through our diets with iodized table salt and iodine-fortified foods.
A 2018 study found that 85% of children receiving parenteral nutrition (given elsewhere in the body other than the mouth) were iodine-deficient. Of those children who were deficient in iodine, 33% developed hypothyroidism.
It’s possible for certain over-the-counter medications like cough suppressants and natural supplements to contain iodine, so be sure to read the label if you are concerned about your child’s thyroid function.
Mother’s Hypothyroidism
Hypothyroidism in pregnancy affects about 3% to 5% of mothers and is the most common pregnancy-related thyroid disorder. When a pregnant mother has hypothyroidism, her condition can lead to hypothyroidism in her child. This is because fetuses rely on their mother’s thyroid hormones during their first few months in the uterus. When a mother’s body cannot produce enough hormone, the fetus does not get what they need. Thyroid hormone is important for brain development, so this can lead to serious impairment if left untreated.
Fortunately, women with hypothyroidism can give birth to healthy babies with the help of medications during their pregnancies. If you are currently expecting and concerned about hypothyroidism, talk with your obstetrician about testing your thyroid hormone levels.
Signs and Symptoms
There are several signs and symptoms that point to hypothyroidism in children. Because many of them are vague, such as sleepiness and constipation, it’s helpful to be aware of all the possible symptoms so you can begin to put the pieces together with your child’s pediatrician.
While many of the symptoms are similar to hypothyroidism in adults, some are specific to children, including:
Slowed growth rate Puffy face Poor muscle tone Sleepiness Constipation Swollen hands and feet Mood swings Hoarse cry or voice Heavy menstruation for teenage girls Dry, itchy scalp or skin, and coarse, dry hair Slower reaction time Cold intolerance Enlarged thyroid, resembling a goiter
Diagnosis
If your pediatrician is concerned that your child may be experiencing hypothyroidism, they will start the diagnosis process with a physical exam and blood tests known as a thyroid screening test.
A thyroid screening test involves two lab tests:
Thyroid-stimulating hormone (TSH) measures the amount of hormone produced by the brain that signals the thyroid to start working. Thyroid hormone (T4) measures the level of hormone produced by the thyroid.
When your child’s TSH level is normal but their T4 level is low, they most likely have hypothyroidism. If their TSH level is low, this could mean they are experiencing central hypothyroidism, which is caused by damage to the pituitary gland or hypothalamus in the brain.
If your child’s weight meets the criteria for obesity, your healthcare provider will most likely order lab tests including TSH. While hypothyroidism can lead to weight gain, it is usually not responsible for obesity. Most children with obesity have slightly elevated TSH levels as opposed to a low finding.
Other tests include:
Anti-thyroid antibody levels: This test measures your child’s levels of anti-thyroperoxidase (anti-TPO) and anti-thyroglobulin (TgAb). These antibodies are elevated in autoimmune hypothyroidism and show that your child’s immune system is attacking their thyroid gland. Thyroid ultrasound: An ultrasound is used to examine the size and shape of your child’s thyroid gland. This painless procedure produces images of the thyroid and may be used to diagnose acquired hypothyroidism or congenital hypothyroidism if the healthcare provider suspects that your infant’s thyroid gland is not located in the correct area of the neck.
Treatment
Most cases of hypothyroidism in children are treated with thyroid hormone replacement medication called levothyroxine. This medication comes in the form of a pill and is identical to the T4 hormone in your child’s body. The medication is taken at the same time every day.
Your newborn will most likely be screened within their first 24 to 48 hours of life and then again at their two-week exam with a pediatrician. A review conducted from 2010 to 2016 found that 20% of newborns with hypothyroidism had normal results in their first screening.
Unfortunately, for the little ones, there is no liquid version of levothyroxine. If your child is too young to swallow pills, the medication can be chewed or crushed for consumption. Use a pill grinder to crush the pill, then mix it into breast milk or formula for infants. If your child also takes calcium or iron supplements, don’t give them their thyroid medication with those supplements since they could affect its effectiveness.
As your child grows, their body will start to require higher levels of thyroid hormone. For this reason, your practitioner will watch your child’s growth and continue to order lab tests to monitor their thyroid hormone levels. If your child’s hormone levels start to level off or decrease, your healthcare provider may recommend an increased dosage of levothyroxine.
A Word from Verywell
If you have recently found out that your child has hypothyroidism, you have most likely been feeling overwhelmed, sad, and maybe even guilty. It’s important to remember that this is a relatively common pediatric condition, and it’s not your fault. Fortunately, hypothyroidism is very treatable, and most children who receive treatment are able to reach normal height and development. Stay in frequent contact with your healthcare provider to monitor treatment progress and adjust thyroid medication dosages as needed.
