Hypothyroidism in children

Hypothyroidism is a clinical syndrome caused by decreased production of thyroid hormones or lack of sensitivity to them in tissues.

Hypothyroidism is a deficiency of thyroid hormones. Symptoms of hypothyroidism in young children include poor feeding and failure to thrive. Signs in older children and adolescents are similar to those in adults but also include poor growth, late puberty, or both. Diagnosis of hypothyroidism is based on thyroid function tests (eg, serum thyroxine, thyroid-stimulating hormone ). Treatment of hypothyroidism involves thyroid hormone replacement therapy.

Hypothyroidism in infants and young children may be congenital or neonatal. Congenital hypothyroidism occurs in approximately 1 in 4,000 live births. Most congenital cases are sporadic, but approximately 10-20% are familial. The most common cause of congenital hypothyroidism is dysgenesis, or absence (agenesis), or underdevelopment (hypoplasia) of the thyroid gland. Approximately 10% of congenital hypothyroidism is due to dyshormonogenesis (abnormal production of thyroid hormones), of which there are 4 types. Rarely in the United States but common in some developing countries, hypothyroidism results from maternal iodine deficiency. Rarely, transient hypothyroidism may be caused by transplacental passage of antibodies, goitrogens (eg, amiodarone), or antithyroid drugs (eg, propylthiouracil, methimazole).

ICD-10 code

• E00 Congenital iodine deficiency syndrome.
• E01.0 Diffuse (endemic) goiter associated with iodine deficiency.
• E01.1 Multinodular (endemic) goiter associated with iodine deficiency.
• E01.2 Goiter (endemic) associated with iodine deficiency, unspecified.
• E01.8 Other thyroid diseases associated with iodine deficiency and similar conditions.
• E02 Subclinical hypothyroidism due to iodine deficiency.
• E03.0 Congenital hypothyroidism with diffuse goiter.
• E03.1 Congenital hypothyroidism without goiter.
• E03.2 Hypothyroidism induced by drugs and other exogenous substances.
• E03.3 Post-infectious hypothyroidism.
• E03.5 Myxedema coma.
• E03.8 Other specified hypothyroidisms.
• E03.9 Hypothyroidism, unspecified.

Hypothyroidism in Older Children and Adolescents

The usual cause is autoimmune thyroiditis (Hashimoto's thyroiditis). Some symptoms of hypothyroidism are similar to those of adults (eg, weight gain, obesity; constipation; coarse, dry hair; yellowish, cool, or mottled rough skin). Features typical of children include failure to thrive, delayed skeletal maturation, and usually delayed puberty. Treatment is with L-thyroxine 5 to 6 mcg/kg orally once daily; in adolescents, the dose is reduced to 2 to 3 mcg/kg orally once daily and titrated to maintain serum thyroxine and thyroid-stimulating hormone levels within the normal age range.

Symptoms of Hypothyroidism in Children

The symptoms of hypothyroidism differ from those in adults. If iodine deficiency occurs early in pregnancy, the child may develop endemic cretinism (a syndrome that includes deaf-muteness), mental retardation, and spasticity. In most cases, infants with hypothyroidism have few or no symptoms because the placenta receives thyroid hormones from the mother. However, after the maternal hormones are metabolized, if the underlying cause of hypothyroidism persists, and if hypothyroidism is not diagnosed and treated, moderate to severe CNS developmental delay occurs, which may be accompanied by muscle hypotonia, prolonged hyperbilirubinemia, umbilical hernias, respiratory failure, macroglossia, large fontanelles, hypotrophy, and hoarseness. Rarely, late diagnosis and treatment of severe hypothyroidism leads to mental retardation and short stature.

Classification of hypothyroidism

Congenital and acquired hypothyroidism are distinguished; according to the level of disorder of regulatory mechanisms, primary (pathology of the thyroid gland itself), secondary (pituitary disorders) and tertiary (hypothalamic disorders) are distinguished. A peripheral form of hypothyroidism is also distinguished, associated with a disorder of metabolism of thyroid hormones in tissues or resistance of tissues to them.

[ 1 ], [ 2 ], [ 3 ], [ 4 ], [ 5 ]

Diagnosis of hypothyroidism in children

Routine newborn screening detects hypothyroidism before clinical manifestations become apparent. If the screening result is positive, thyroid function testing, including serum thyroxine (T3), free T4, and thyroid-stimulating hormone (TSH) is indicated.

[ 6 ], [ 7 ]

Treatment of hypothyroidism in children

In most cases, lifelong thyroid hormone replacement therapy is required. Treatment of hypothyroidism in children with L-thyroxine 10-15 mcg/kg orally once daily should be started immediately and monitored at frequent intervals. This dose is intended to rapidly normalize serum T levels and should then be titrated to maintain serum T levels within 10-15 mcg/dL during the first years of life. In the second year of life, the usual dose is 5-6 mcg/kg orally once daily, which should maintain serum T and TSH levels within the normal age range. Most treated children have normal motor and mental development. Severe congenital hypothyroidism in children, even with adequate treatment, may still cause minor developmental problems and sensorineural hearing loss. Hearing impairment may be so subtle that it may not be detected by initial screening. A repeat examination at 1-2 years is recommended to detect hidden hearing defects that may affect speech development. Thyroxine-binding globulin deficiency, which is detected during a screening examination based primarily on the determination of thyroxine, does not require treatment, since children with this condition are euthyroid.