Hypothyroidism in children usually occurs when there is a structural problem with the thyroid gland or the thyroid gland is inflamed.
Symptoms depend on the child's age but include delayed growth and development.
The diagnosis is based on newborn screening tests, blood tests, and imaging tests.
Treatment includes giving thyroid hormone replacement.
(See also Hypothyroidism Hypothyroidism Hypothyroidism is underactivity of the thyroid gland that leads to inadequate production of thyroid hormones and a slowing of vital body functions. Facial expressions become dull, the voice... read more in adults and Hypothyroidism in the Newborn Hypothyroidism in the Newborn Hypothyroidism is decreased production of thyroid hormone. Hypothyroidism in the newborn may occur if there is a structural problem with the thyroid gland. Symptoms may include delayed growth... read more .)
The thyroid gland is an endocrine gland Endocrine Glands The endocrine system consists of a group of glands and organs that regulate and control various body functions by producing and secreting hormones. Hormones are chemical substances that affect... read more located in the neck. Endocrine glands secrete hormones into the bloodstream. Hormones Endocrine Function The main function of endocrine glands is to secrete hormones directly into the bloodstream. Hormones are chemical substances that affect the activity of another part of the body (target site)... read more are chemical messengers that affect the activity of another part of the body.
Locating the Thyroid Gland
The thyroid gland Overview of the Thyroid Gland The thyroid is a small gland, measuring about 2 inches (5 centimeters) across, that is located just under the skin in the neck. The two halves (lobes) of the gland are connected in the middle... read more secretes thyroid hormone. Thyroid hormone controls the speed of the body's metabolism, including how fast the heart beats and how the body regulates temperature. If the thyroid gland does not produce enough thyroid hormone, these functions slow down.
There are two types of hypothyroidism in infants and children:
Congenital hypothyroidism: Present at birth
Acquired hypothyroidism: Develops after birth
Congenital hypothyroidism occurs when the thyroid gland does not develop or function normally before birth (see Hypothyroidism in the Newborn Hypothyroidism in the Newborn Hypothyroidism is decreased production of thyroid hormone. Hypothyroidism in the newborn may occur if there is a structural problem with the thyroid gland. Symptoms may include delayed growth... read more ). This type of hypothyroidism occurs in about 1 in 1,700 to 3,500 live births. Most cases occur spontaneously, but about 10 to 20% are inherited.
About half of cases of congenital hypothyroidism occur because the thyroid gland is missing, underdeveloped, or developed in the wrong place. Less often, the gland has developed normally but does not produce thyroid hormone correctly.
Congenital hypothyroidism can occur if the mother did not have enough iodine in her diet while pregnant (iodine deficiency Iodine Deficiency Iodine deficiency, which is common worldwide, can lead to enlargement of the thyroid gland. (See also Overview of Minerals.) Iodine occurs in seawater. A small amount of iodine from seawater... read more ), because a woman's body needs more iodine when she is pregnant. Iodine deficiency is rare in areas of the world where iodine is added to table salt but is more common in areas where people do not get enough iodine in their diet. Another rare cause is central hypothyroidism. Central hypothyroidism is caused by structural problems that occur in the pituitary gland while it is developing (see Overview of the Pituitary Gland Overview of the Pituitary Gland The pituitary is a pea-sized gland that is housed within a bony structure (sella turcica) at the base of the brain. The sella turcica protects the pituitary but allows very little room for expansion... read more ).
Rarely, drugs that are used to treat thyroid disorders or substances in foods cross the placenta and temporarily cause congenital hypothyroidism.
Acquired hypothyroidism occurs after birth.
In the United States, acquired hypothyroidism is most commonly caused by Hashimoto thyroiditis Down Syndrome (Trisomy 21) Down syndrome is a chromosome disorder caused by an extra chromosome 21 that results in intellectual disability and physical abnormalities. Down syndrome is caused by an extra chromosome 21... read more (autoimmune thyroiditis). In Hashimoto thyroiditis, the body's immune system attacks the cells of the thyroid gland, causing chronic inflammation and decreased production of thyroid hormones. About 50% of affected children have a family history of autoimmune thyroid disease. Autoimmune thyroiditis occurs most commonly during adolescence, but it can also occur in younger children, typically after the first few years of life. Children who have Down syndrome Down Syndrome (Trisomy 21) Down syndrome is a chromosome disorder caused by an extra chromosome 21 that results in intellectual disability and physical abnormalities. Down syndrome is caused by an extra chromosome 21... read more are at increased risk of autoimmune thyroiditis.
Worldwide, the most common cause of hypothyroidism is iodine deficiency, but this cause is rare in the United States. However, pregnant women in the United States can develop mild iodine deficiency because their bodies need more iodine when they are pregnant. Children who have multiple food allergies or who are following restrictive diets may not eat enough of the proper foods and thus develop iodine deficiency.
Other less common causes of acquired hypothyroidism include radiation therapy to the head and neck for certain cancers and the use of certain drugs (for example, lithium or amiodarone). Hypothyroidism also occurs as a result of treatment for hyperthyroidism Treatment Hyperthyroidism is increased production of thyroid hormone. Graves disease is the usual cause of hyperthyroidism, but growths (nodules) on or inflammation of the thyroid gland, drugs, and infections... read more or for thyroid cancer Types of Thyroid Cancer The cause of thyroid cancer is not known, but the thyroid gland is very sensitive to radiation, which may cause cancerous changes. Thyroid cancer is more common among people who were treated... read more .
Symptoms of hypothyroidism differ depending on the age of the child.
Infants and young children
If iodine deficiency occurs very early during pregnancy, infants may have severe growth failure, abnormal facial features, intellectual disability, and stiff muscles that are difficult to move and control (called spasticity).
Most other infants who have hypothyroidism initially have few if any symptoms because some thyroid hormone from the mother crosses the placenta. Once infants no longer receive thyroid hormone from the mother, symptoms develop slowly and the disease is detected only when they are screened as newborns.
However, if hypothyroidism remains untreated, brain development slows and infants may have low muscle tone, hearing loss, a large tongue, poor feeding, and hoarse crying. Delayed diagnosis and treatment of severe hypothyroidism can lead to intellectual disability Intellectual Disability Intellectual disability is significantly below average intellectual functioning present from birth or early infancy, causing limitations in the ability to conduct normal activities of daily... read more and short stature Growth Hormone Deficiency in Children Growth hormone deficiency occurs when the pituitary gland does not produce enough growth hormone. Growth hormone deficiency is the most common pituitary hormone deficiency and is accompanied... read more .
Older children and adolescents
Some symptoms in older children and adolescents are similar to symptoms of hypothyroidism in adults Symptoms Hypothyroidism is underactivity of the thyroid gland that leads to inadequate production of thyroid hormones and a slowing of vital body functions. Facial expressions become dull, the voice... read more (such as weight gain; fatigue; constipation; coarse, dry hair; and coarse, dry, and thick skin). Symptoms that appear only in children include slowed growth, a delay in the development of the skeleton, and delayed puberty Delayed Puberty Delayed puberty is defined as absence of the start of sexual maturation at the expected time. Most often, children simply develop later than their peers but ultimately develop normally. Sometimes... read more .
Newborn screening test
Sometimes imaging tests
Because infants with hypothyroidism at birth often do not have any abnormal findings, doctors do routine screening tests of all newborns Newborn Screening Tests Screening tests are done to detect health conditions that are not yet causing symptoms. Many serious disorders that are not apparent at birth can be detected by various screening tests. Early... read more . If the screening is positive, tests to determine levels of thyroid hormones in the blood (thyroid function tests Thyroid function blood tests The thyroid is a small gland, measuring about 2 inches (5 centimeters) across, that is located just under the skin in the neck. The two halves (lobes) of the gland are connected in the middle... read more ) are done to confirm the diagnosis of hypothyroidism. If confirmed, newborns must be treated quickly to prevent developmental delays.
Once congenital hypothyroidism is diagnosed, doctors may do imaging tests such as radionuclide scanning Radionuclide Scanning Radionuclide scanning is a type of medical imaging that produces images by detecting radiation after a radioactive material is administered. During a radionuclide scan, a small amount of a radionuclide... read more or ultrasonography Ultrasonography Ultrasonography is a type of medical imaging that uses high-frequency sound (ultrasound) waves to produce images of internal organs and other tissues. During an ultrasound, a device called a... read more to determine the size and location of the thyroid gland.
Thyroid function tests are also done in older children and adolescents who doctors think may have hypothyroidism. Biotin is a common over-the-counter supplement that can interfere with thyroid function tests by causing false readings of certain hormones. Use of biotin should be stopped for at least 2 days before tests are done. Ultrasonography may also be done if the thyroid gland feels asymmetric or the doctor feels a growth (nodule) on the thyroid gland.
Doctors do magnetic resonance imaging Magnetic Resonance Imaging (MRI) Magnetic resonance imaging (MRI) is a type of medical imaging that uses a strong magnetic field and very high frequency radio waves to produce highly detailed images. During an MRI, a computer... read more (MRI) of the brain and pituitary gland in children who have central hypothyroidism to rule out problems in the brain.
Most children who are treated during infancy have normal movement control and intellectual development.
Most children with hypothyroidism who properly take their drugs achieve normal growth and development.
Replacement of thyroid hormone
Children who have congenital or acquired hypothyroidism are usually given the synthetic thyroid hormone levothyroxine. Thyroid hormone replacement usually is given to children in tablet form. For infants, tablets can be crushed, mixed with a small amount (1 to 2 milliliters) of water, breast milk, or non–soy-based formula, and given by mouth by syringe. It should not be given simultaneously with soy formula, or iron or calcium supplements because these substances can decrease the amount of replacement thyroid hormone that is absorbed. Liquid formulations are available commercially for children of any age, but there is limited experience with the use of these formulations in the treatment of congenital hypothyroidism.
Most children who have congenital or acquired hypothyroidism need to take thyroid hormone replacement for life. However, some children who have congenital hypothyroidism, usually those who have not required a dose increase after infancy, may be able to stop treatment after they are about 3 years of age.
Doctors continue to monitor children by doing blood tests at regular intervals depending on their age. Children are monitored more frequently during the first few years of life.