Thyroid Hormone Administration Pediatric Endocrine Society

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 Hormone Administration

Thyroid function tests are also done in older children and adolescents in whom hypothyroidism is suspected. Levothyroxine is typically given in tablet form because of the inconsistent delivery of compounded liquid formulations prepared by individual pharmacists. Tablets can be crushed, mixed with a small amount (1 to 2 mL) of water, breast milk, or non–soy-based formula, and given orally by syringe. The absorption oflevothyroxine may be decreased if it is given with soy formula, iron, or calcium. 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.

What is Thyroid Hormone?

Babies and older children also need thyroid hormone for normal growth, among other important body functions. In some countries, congenital hypothyroidism occurs when the mother does not get enough iodine in her diet while pregnant (iodine deficiency), and a woman’sbody 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.

Children who have Down syndrome are at increased risk of congenital hypothyroidism. Eventually, infants may develop dry, cool, mottled skin, coarse facial features (such as a flat, broad nasal bridge and a puffy face), and a slightly open mouth with an enlarged tongue. Hypothyroidism can occur in a developing fetus or newborn or during synthroid phentermine childhood or adolescence. Once-daily administration and close follow-up with your endocrinologist is needed to ensure the best possible results. Dyshormonogenesis has multiple types, which can result from a defect in any of the steps of thyroid hormone biosynthesis (see Congenital Goiter). Copyright © 2018 American Academy of Pediatrics and Pediatric Endocrine Society.

Locating the Thyroid Gland

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.

• Children who have Down syndrome or Turner syndrome are at increased risk of Hashimoto thyroiditis.
• 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.
• Eventually, infants may develop dry, cool, mottled skin, coarse facial features (such as a flat, broad nasal bridge and a puffy face), and a slightly open mouth with an enlarged tongue.
• 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.

Severe congenital hypothyroidism, even when treated promptly, may still cause subtle developmental problems and sensorineural hearing loss (3, 4). Hearing loss may be so mild that initial screening misses it, but it may still interfere with language acquisition. For babies and small children, because there is no reliable liquid preparation, the pill should be crushed just before administration and mixed with a small volume of water, human (breast) milk, or formula. This mixture can be given to the baby or small child using a spoon, dropper, or infant syringe.

• The absorption oflevothyroxine may be decreased if it is given with soy formula, iron, or calcium.
• Thyroid function tests are also done in older children and adolescents in whom hypothyroidism is suspected.
• 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.
• Diagnosis is by thyroid function testing (eg, serum thyroxine, thyroid-stimulating hormone).
• Worldwide, the most common cause of hypothyroidism is iodine deficiency, but this cause is rare in the United States.

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 gland has developed normally but does not produce normal amounts of thyroid hormone.

In the United States, acquired hypothyroidism is most commonly caused by Hashimoto thyroiditis (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. Hashimoto 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 or Turner syndrome are at increased risk of Hashimoto thyroiditis. 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.

Symptoms and Signs of Hypothyroidism in Infants and Children

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).

Children confirmed to have central hypothyroidism should have MRI of the brain and pituitary to rule out central nervous system lesions. 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). For children with euthyroid sick syndrome, thyroid function normalizes as the clinical status improves. Even when treated promptly, severe congenital hypothyroidism may still cause subtle developmental problems and hearing loss. Hearing loss may be so mild that it is not detected during the routine newborn screening, but it may still interfere with language learning.