Hypothyroidism in Infants and Children Children’s Health Issues

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.

This regimen is intended to rapidly (within 2 weeks) bring the serum T4 level into the upper half of the normal range for age (between 10 mcg/dL 129 nmol/L and 15 mcg/dL 193 nmol/L) and promptly (within 4 weeks) reduce the TSH. More than half of cases of congenital hypothyroidism occur because the thyroid gland is missing, underdeveloped, or developed in the wrong place. Less often, the synthroid warfarin gland has developed normally but does not produce normal amounts of thyroid hormone.

Is it OK To Switch Between Brands of Thyroid Hormone Medication?

There is controversy regarding treatment of patients with subclinical hypothyroidism. Treatment can be considered if patients have a goiter, positive thyroid antibodies, decreased growth velocity, or hyperlipidemia. If not treated, thyroid function should be monitored every 6 to 12 months for a period of time to make sure function does not worsen. Thyroid testing should be repeated in patients with subclinical hypothyroidism because the majority of patients will have normalized TSH levels on repeat testing (1).

Symptoms of Hypothyroidism in Infants and Children

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).

Etiology of Hypothyroidism in Infants and Children

Thyroid hormone is the medication prescribed by your child’s doctor to treat hypothyroidism, also known as an underactive thyroid gland. The body makes 2 forms of thyroid hormone, levothyroxine (T4) and triiodothyronine (T3). Generally, prescribed thyroid hormone comes in the form of T4, which is converted by the body to the active form, T3. Brand names you may encounter for this medication include Levothroid, Levoxyl, Synthroid, and Unithroid. Babies who need thyroid hormone because of hypothyroidism must be given this medication on a regular basis so that their brains will develop normally.

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.

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.

Once congenital hypothyroidism is diagnosed, doctors may do imaging tests such as radionuclide scanning or ultrasonography to determine the size and location of the thyroid gland. You do not need to worry about thyroid hormones interacting with other medications, as the medicine simply replaces a hormone that your child is no longer able to make. A good way to keep track of your child’s doses is to get a 7-day pillbox and fill it at the beginning of the week.

• Thyroid function tests are also done in older children and adolescents who doctors think may have hypothyroidism.
• Children who have other genetic conditions (such as DiGeorge syndrome or Prader-Willi syndrome) are at increased risk of acquired hypothyroidism that is not autoimmune.
• At first, newborns who have hypothyroidism that is caused by a problem with their thyroid gland usually have few if any symptoms because some thyroid hormone from the mother crosses the placenta.
• Hashimoto thyroiditis occurs most commonly during adolescence, but it can also occur in younger children, typically after the first few years of life.
• Alternatively this pattern of thyroid dysfunction develops in children who use certain medications (eg, antiseizure medications, immune checkpoint inhibitors) or who have certain illnesses (euthyroid sick syndrome).

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.

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.