Hypothyroidism in Infants and Children Children’s Health Issues

Hypothyroidism also occurs as a result oftreatment for hyperthyroidism or for thyroid cancer. Congenital hypothyroidism occurs when the thyroid gland does not develop or function normally before birth. In acquired hypothyroidism, the usual starting dose of levothyroxine often depends on degree of hypothyroidism at diagnosis. For severe, longstanding hypothyroidism, lower starting doses may be selected to avoid potential behavioral symptoms with slower titration to full dosing. Thyroid ultrasonography is not necessary to establish the diagnosis of autoimmune thyroiditis and should be restricted to children with thyroid gland asymmetry or palpable thyroid nodules.

Conditions & Treatments

Symptoms in infants include poor feeding and growth failure; symptoms in older children and adolescents are similar to those of adults but also include growth failure, delayed puberty, or both. Diagnosis is by thyroid function testing (eg, serum thyroxine, thyroid-stimulating hormone). 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. Ultrasonography may also be done in older children and adolescents if the thyroid gland feels asymmetric or the doctor feels a growth (nodule) on the thyroid gland. Older children who have only slight elevations in TSH (typically between 5 mU/L and 10 mU/L) and normal free T4 levels are considered to have subclinical hypothyroidism.

Of note, patients with obesity may have subclinical hypothyroidism, but this is thought to be an adverse effect of obesity as opposed to a cause. Treatment is not recommended unless other factors (eg, positive thyroid antibodies, goiter) are present. Symptoms and signs of hypothyroidism in infants and young children differ from those in older children and adults. If fetal iodine deficiency occurs very early during pregnancy, infants may present with severe growth failure, coarse facial features, intellectual disability, and spasticity. Central hypothyroidism manifests with a pattern of low free T4 and non-elevated TSH levels. Central hypothyroidism may manifest in children with midline defects (eg, cleft palate, microphallus) or visual impairments (eg, nystagmus).

Symptoms of Hypothyroidism in Infants and Children

If you find out one day that the previous dose was missed, it is fine to double the dose the next day. Most children with hypothyroidism who properly take their medications achieve normal growth and development. Doctors do magnetic resonance imaging (MRI) of the brain and pituitary gland in children who have central hypothyroidism to rule out problems in the brain. Some symptoms in older children and adolescents are similar to symptoms of hypothyroidism in adults (such as weight gain; fatigue; constipation; coarse, dry hair; and coarse, dry, and thick skin). Measurement of triiodothyronine (T3) levels is rarely helpful in the diagnosis of hypothyroidism because it is the last test to show abnormal results and should not be done in most patients. Reverse T3 levels measure the metabolically inactive form of T3; reverse T3 increases during periods of illness or starvation and should not be measured to diagnose hypothyroidism.

Symptoms that do occur may be subtle or develop slowly because some maternal thyroid hormone crosses the placenta. Rarely, delayed diagnosis and treatment of severe hypothyroidism lead to intellectual disability and short stature. Permanent hypothyroidism is also the goal of therapy for patients undergoing definitive therapy for Graves disease (see treatment of hyperthyroidism in infants and children) or thyroid cancer. Rarely in the United States but commonly in countries where iodine is not routinely added to table salt, hypothyroidism results from maternal iodine deficiency. Rarely, transplacental transfer of antibodies, goitrogens (eg, amiodarone), or antithyroid medications (eg, propylthiouracil, methimazole) causes transient hypothyroidism.

Diagnosis of Hypothyroidism in Infants and Children

• Treatment is not recommended unless other factors (eg, positive thyroid antibodies, goiter) are present.
• If the screening is positive, tests to determine levels of thyroid hormones in the blood (thyroid function tests) are done to confirm the diagnosis of hypothyroidism.
• Children with trisomy 21 and Turner syndrome are at increased risk of autoimmune thyroid disease.
• For both forms of hypothyroidism, the dose is titrated to maintain serum T4 and TSH levels within the normal range for age.

The information contained in this publication should not be used as a substitute for the medical care and advice of your pediatrician. There may be variations in treatment that your pediatrician may recommend based on individual facts and circumstances.

Etiology of Hypothyroidism in Infants and Children

• The rare side effects of thyroid hormone medication are related to overdose, or too much medication, and can include rapid heart rate, sweating, anxiety, and tremors.
• Commercial oral liquid formulations are available for children of any age and are available as single-dose ampules in different strengths or as 100-mL bottles with the dose selected by syringe volume.
• Dyshormonogenesis has multiple types, which can result from a defect in any of the steps of thyroid hormone biosynthesis (see Congenital Goiter).
• If screening is positive, confirmation is necessary with thyroid function tests, including measurement of free serum thyroxine (free T4) and thyroid-stimulating hormone (TSH) (2).
• Children who have congenital or acquired hypothyroidism are usually given the synthetic thyroid hormone levothyroxine.Levothyroxineusually is given to children in tablet form.

Another rare cause is central hypothyroidism, which is caused by structural anomalies in pituitary development; patients usually also have other pituitary hormone deficiencies. Signs specific to children are growth retardation, delayed skeletal maturation, and usually delayed puberty. Autoimmune thyroiditis occurs most commonly during adolescence, but it also occurs in younger children, typically after the first few years of life. Children with trisomy 21 and effexor synthroid Turner syndrome are at increased risk of autoimmune thyroid disease. Children with other genetic conditions (eg, DiGeorge syndrome, Prader-Willi syndrome) are at increased risk of acquired hypothyroidism that is not autoimmune.

Biotin, a common over-the-counter supplement, should be stopped for at least 2 days before laboratory testing because it can interfere with several thyroid function tests. Most commonly, biotin can result in falsely high levels of T4 and T3 and falsely low levels of TSH and can lead to an inappropriate diagnosis of hyperthyroidism (5). Children who have congenital or acquired hypothyroidism are usually given the synthetic thyroid hormone levothyroxine.Levothyroxineusually 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 with iron or calcium supplements because these substances can decrease the amount of levothyroxine 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.

Older children and adolescents

Iodine deficiency remains the most common worldwide cause of hypothyroidism in children but is rare in the United States. Iodine deficiency may occur in children whose diet is restricted because of multiple food allergies or in those who require long-term parenteral nutrition. Treatment of hypothyroidism is directed by a doctor who specializes in treating children with problems of the endocrine system (called a pediatric endocrinologist). Doctors continue to monitor children by doing blood tests at regular intervals depending on their age.

• For children with euthyroid sick syndrome, thyroid function normalizes as the clinical status improves.
• Symptoms that appear only in children include slowed growth, a delay in the development of the skeleton, and delayed puberty.
• Signs specific to children are growth retardation, delayed skeletal maturation, and usually delayed puberty.

Treatment regimens

Symptoms that appear only in children include slowed growth, a delay in the development of the skeleton, and delayed puberty. Older children can be monitored more frequently if there are concerns about adherence. After a dose adjustment in older children, TSH and free T4 levels are measured in 6 to 8 weeks. Most other hypothyroid infants initially have few if any symptoms or signs and are detected only through newborn screening. Most newborns who are treated have normal movement control and intellectual development. Hormones are chemical messengers that affect the activity of another part of the body.