Thyroid Hormone Administration Pediatric Endocrine Society

If iodine deficiency occurs very early during pregnancy, newborns may have severe growth failure, abnormal facial features, intellectual disability, and stiff muscles that are difficult to move and control (called spasticity). If the underlying cause of hypothyroidism is not identified and hypothyroidism remains undiagnosed or untreated, brain development slows moderately to severely. If the newborn has an enlarged thyroid gland (congenital goiter), the gland may press against the windpipe and interfere with breathing.

What Are the Side Effects of Thyroid Hormone Medication?

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.

Conditions & Treatments

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 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.

• The information contained in this publication should not be used as a substitute for the medical care and advice of your pediatrician.
• 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.
• Treatment is not recommended unless other factors (eg, positive thyroid antibodies, goiter) are present.
• 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 with trisomy 21 and Turner syndrome are at increased risk of autoimmune thyroid disease.

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.

To date, there is limited experience with these liquid formulations in congenital hypothyroidism, and it is unclear whether dosing is the same as for crushed tablets. If levothyroxinemust be given intravenously, 75% of the oral dose should be used. Although T3 is the biologically active thyroid hormone, levothyroxine (T4) is usually given as monotherapy and it is not necessary to use T3 because the majority of brain T3 arises through enzyme conversion of T4 to T3. In children and adolescents with suspected hypothyroidism (elevated TSH and low T4/free T4), thyroid antibody titers (to thyroid peroxidase and thyroglobulin) should be measured to evaluate for autoimmune thyroiditis.

• A child will not have these problems if the thyroid hormone dose prescribed is only slightly more than is needed.
• Signs specific to children are growth retardation, delayed skeletal maturation, and usually delayed puberty.
• Symptoms that appear only in children include slowed growth, a delay in the development of the skeleton, and delayed puberty.

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

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.

For those who have an illness, thyroid function becomes normal once the illness goes away. synthroid sleeplessness Routine newborn screening detects hypothyroidism before clinical signs are evident (1). 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). Free T4 is a better measure of thyroid function than total T4 in these patients because the levels of thyroid-binding proteins (thyroid-binding globulin, transthyretin, and albumin) affect total T4 levels. It is particularly important to measure free T4 rather than total T4 in preterm or low birthweight infants in whom alterations in binding proteins lead to low total T4 levels despite normal free T4 levels.

The spoon, dropper, or syringe should be “washed through” with more liquid 2 more times until all the thyroid hormone has been given. Making a mixture of crushed tablets and water or formula for storage is not recommended because this preparation is not stable. Some pharmacies will prepare a compounded suspension of levothyroxine, but it is only guaranteed to be stable for a month and it is more expensive. Other less common causes of acquired hypothyroidism include radiation therapy to the head and neck for certain cancers and the use of certain medications (for example, lithium or amiodarone).

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’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.

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.