pediatrics
Hypothyroidism in Infants and Children
Etiology
Hypothyroidism in infants and young children may be congenital or acquired. Congenital hypothyroidism occurs in about 1/1700 to 1/3500 live births ( Etiology reference ). Most congenital cases are sporadic, but about 10 to 20% are inherited. Causes include Dysgenesis of the gland (50 to 60% of cases) Dyshormonogenesis (abnormal thyroid hormone production, 30 to 40% of cases) Dysgenesismay involve ectopy (two thirds of cases), absence (agenesis), or underdevelopment (hypoplasia) of the thyroid gland. The cause is usually unknown, but an estimated 2 to 5% of cases are inherited, often in genes associated with thyroid gland formation (TSHR) or transcription factors (PAX8,NKX2-1). has multiple types, which can result from a defect in any of the steps of thyroid hormone biosynthesis ( see Congenital Goiter ). Rarely in the US 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, Themost common causeof acquired hypothyroidism in the US is Autoimmune thyroiditis ( Hashimoto Thyroiditis ) Autoimmune thyroiditis occurs most commonly during adolescence, but it also occurs in younger children, typically after the first few years of life. About 50% of affected children have a family history of autoimmune thyroid disease. Children with Down Syndrome (Trisomy 21) are at increased risk of autoimmune thyroid disease. , tyrosine kinase inhibitors). Permanent hypothyroidism is also the goal of therapy for patients undergoing definitive therapy for Graves disease (see Treatment ) or Iodine Deficiency remains the most common worldwide cause of hypothyroidism in children but is rare in the US. Iodine deficiency may occur in children whose diet is restricted because of multiple food allergies or in those who require long-term parenteral nutrition. 1.Ford G, LaFranchi SH: Screening for congenital hypothyroidism: A worldwide view of strategies.Best Pract Res Clin Endocrinol Metab28(2):175–187, 2014. doi: 10.1016/j.beem.2013.05.008 