Hyperthyroidism in Infants and Children
Hyperthyroidism is increased production of thyroid hormone.
Graves disease is the usual cause of hyperthyroidism, but growths on or inflammation of the thyroid gland, drugs, and infections can be causes too.
Symptoms depend on the child's age but typically include speeding up of bodily functions.
The diagnosis is based on blood tests and imaging tests.
Infants who are not treated until birth may have intellectual disability, growth failure, and short stature, and some may die.
Treatment typically includes antithyroid drugs and beta-blockers.
(For adults, see also Hyperthyroidism.)
The thyroid gland is an endocrine gland located in the neck. Endocrine glands secrete hormones into the bloodstream. Hormones are chemical messengers that affect the activity of another part of the body.
The thyroid gland 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 produces too much thyroid hormone, these functions speed up.
Hyperthyroidism can occur in a developing fetus or infant (see Hyperthyroidism in the Newborn) or during childhood or adolescence.
Hyperthyroidism is rare in infants but can be life-threatening. It develops in fetuses of women who have or have had Graves disease. In Graves disease, abnormal antibodies stimulate the thyroid gland to produce excess thyroid hormone. These antibodies may cross the placenta and stimulate the thyroid gland in the fetus, which may cause premature birth or even death. Because infants are no longer exposed to the mother's antibodies after birth, Graves disease in the newborn (neonatal Graves disease) is usually temporary but the duration varies.
The cause of hyperthyroidism in more than 90% of children and adolescents is Graves disease.
Less common causes include growths (nodules) on the thyroid gland, inflammation of the thyroid gland (thyroiditis in which hyperthyroidism is temporary, being followed by hypothyroidism), and some drugs. Occasionally, temporary hyperthyroidism can be caused by infections, including bacterial (acute thyroiditis) and viral (subacute thyroiditis) infections.
Symptoms of hyperthyroidism differ depending on the age of the child.
Symptoms of hyperthyroidism in fetuses may appear as early as the second trimester. Affected fetuses have poor growth, a very fast heart rate, and an enlarged thyroid gland (goiter). If the disorder is present and untreated for a long period before birth, about 15% of infants die and others have impaired intellectual development, poor growth, and short stature.
In infants, symptoms include irritability, feeding problems, high blood pressure, fast heart rate, bulging eyes, congenital goiter, and skull abnormalities. Other symptoms include failure to thrive, vomiting, and diarrhea.
Symptoms of hyperthyroidism reflect the speeding up of bodily functions:
Although bodily functions increase, concentration and school performance decrease. Goiter may be present. Children may have red or bulging eyes.
Symptoms of acute thyroiditis develop suddenly. Children have tenderness over the thyroid gland, and fever. In subacute thyroiditis, these symptoms are present but are less severe and may begin after a viral illness. Fever may last for several weeks.
Thyroid storm is a rare, severe complication of hyperthyroidism and a life-threatening emergency. In thyroid storm, the thyroid gland becomes suddenly and extremely active. All body functions are accelerated to dangerously high levels. Symptoms in affected children include an extremely fast heart rate, high body temperature, high blood pressure, heart failure, and changes in mental status. This disorder can lead to coma and death.
In infants, doctors suspect the diagnosis of hyperthyroidism if the mother has active Graves disease or a history of Graves disease and high levels of thyroid-stimulating antibodies. To confirm the diagnosis, doctors do tests to determine levels of thyroid hormones in the blood (thyroid function tests).
In older children and adolescents, doctors do thyroid function tests. Doctors also do ultrasonography on older children who have Graves disease if the thyroid gland feels asymmetric or they feel a growth (nodule) on the thyroid gland. If a nodule is found during ultrasonography, doctors remove a piece of it using a needle (called fine-needle aspiration biopsy) to determine whether the child has thyroid cancer. Doctors may also do radionuclide scanning to see whether the nodule is the source of the excess thyroid hormone.
Infants who developed hyperthyroidism as a fetus may be severely affected if hyperthyroidism is not detected until birth. The space between their skull bones may close too soon (called craniosynostosis) and they may have intellectual disability, growth failure, and short stature. About 10 to 15% of infants may die.
Infants who have neonatal Graves disease almost always recover within 6 months. If the mother did not take drugs that decrease the gland's production of thyroid hormones (antithyroid drugs) while pregnant, infants have hyperthyroidism at birth. If the mother is taking drugs, infants may not show symptoms of hyperthyroidism for about 3 to 7 days.
Older children who have Graves disease may respond to antithyroid drugs or may need additional treatments to permanently treat the disorder if antithyroid drugs are not effective or if symptoms return.
Children are given antithyroid drugs (such as methimazole) which decrease the thyroid gland's production of thyroid hormones. Beta-blockers are drugs that slow the heart rate and are used only if the heart rate is too fast or blood pressure is too high. Treatment with beta-blockers is stopped after the antithyroid drugs have taken effect. Infants who have neonatal hyperthyroidism almost always recover by 6 months and no longer need antithyroid drugs. Symptoms in older children treated with antithyroid drugs may eventually disappear (called remission), but symptoms may return (called relapse) in some children and they may need further treatment.
Sometimes children with Graves disease need additional treatments to permanently treat the disorder. Permanent treatment (definitive therapy) may be needed if the antithyroid drugs do not work (or the child does not take them) or if the drugs are causing serious side effects. In definitive therapy, the gland is destroyed with radioactive iodine or surgery. However, radioactive iodine is usually not given to children who are under age 10 and is often not effective in people who have larger thyroid glands. Therefore, surgery may be done instead for children and adolescents who have these factors.
Nodules are removed surgically.
Acute thyroiditis is treated with antibiotics. Subacute thyroiditis is not treated with antibiotics, but nonsteroidal anti-inflammatory drugs (NSAIDs) are given for pain. Children are not given antithyroid drugs, but beta-blockers may be given.