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Goiter can present at any age in children. The most common cause of goiter formation in the United States is autoimmune thyroiditis. In neonates, the normal thyroid size has been reported as 0.9 ± 0.2 mL. In older children from iodine sufficient areas, it is 3.1 to 6.3 mL. The “rule of thumb” is also used to determine thyroid size: each lobe should be the size of the terminal phalanx of the child’s thumb.
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Goiter in the Neonatal Period
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The most common cause of goiter in neonates is congenital hypothyroidism caused by thyroid dyshormonogenesis or inborn errors of thyroid hormone production, as described in Chapter 520. These defects can cause varying degrees of thyroid dysfunction and can present with goiter at birth. They are inherited in an autosomal recessive fashion and account for 10% to 15% of cases of congenital hypothyroidism.
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Goiter formation in this age group can be caused by passage of thyroid antibodies through the placenta. In mothers with autoimmune thyroid disease, either Hashimoto thyroiditis or Graves disease, antibodies can cross the placenta and cause thyroid dysfunction or goiter in the fetus. These antibodies can block or stimulate the thyroid-stimulating hormone (TSH) receptor.
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Blocking antibodies can cause fetal hypothyroidism and also goiter. The condition is transient since these antibodies are usually cleared by 3 to 6 months of age.
Stimulating antibodies can cause fetal and neonatal Graves disease with or without goiter. Often these goiters are detected during prenatal ultrasonography. Again, this condition is usually transient as antibodies tend to clear by 3 to 6 months of age.
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Rarely, neonatal goiter can be caused by activating mutations of the TSH receptor; these germline mutations are inherited in an autosomal dominant fashion and can cause hyperthyroidism and goiter in the neonatal period or later in life. Thionamides can be effective to alleviate the symptoms of hyperthyroidism; however, permanent treatment such as ablation or thyroidectomy needs to be eventually considered.
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McCune-Albright syndrome is characterized by café-au-lait spots, precocious puberty, and polyostotic fibrous dysplasia. It is caused by activating mutations of the G-protein alpha subunit, which can potentially activate each G-protein receptor including the thyroid. Since they are activating mutations, they can lead to thyroid hyperplasia, nodules, and toxic nodular goiters. Hyperthyroidism, if present, will be lifelong and needs permanent treatment such as ablation or thyroidectomy. The features of the syndrome can present later in life but have been reported in the neonatal period.
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Antithyroid drugs and other medications (that are rich in iodine such as amiodarone and nutritional supplements) can cross the placenta and can cause hypothyroidism and goiter in the fetus.
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Goiter in Children and Adolescents
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As mentioned above, the most common cause of goiter in children in the United States is autoimmune thyroid disease.