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Hyperthyroidism is excessive thyroid hormone production. Diagnosis is by thyroid function testing (eg, free serum thyroxine, thyroid-stimulating hormone). Treatment is with propylthiouracil or methimazole.
Etiology
Hyperthyroidism is rare in infants but potentially life-threatening. It develops in fetuses of women with current or prior Graves' disease who have elevated titers of thyroid-stimulating immunoglobulins, which overstimulate thyroid hormone production by binding to thyroid-stimulating hormone (TSH) receptors in the thyroid gland. These antibodies cross the placenta and cause thyroid hyperfunction in the fetus (intrauterine Graves' disease), which can result in fetal death or premature birth. Because infants clear the antibodies after birth, neonatal Graves' disease is usually transient. However, because the clearance rate varies, duration of neonatal Graves' disease varies. In children and adolescents, Graves' disease is the usual cause of hyperthyroidism.
Symptoms and Signs
Symptoms and signs in infants include irritability, feeding problems, hypertension, tachycardia, exophthalmos, goiter, frontal bossing, and microcephaly. Other early findings are failure to thrive, vomiting, and diarrhea. Affected infants almost always recover within 6 mo; the course is rarely longer. Persistent hyperthyroidism may result in craniosynostosis (premature fusion of the cranial sutures), impaired intellect, growth failure, short stature, and hyperactivity later in childhood. Mortality rate may reach 10 to 15%. In children and adolescents, acquired Graves' disease is characterized by diffuse goiter, thyrotoxicosis, and, rarely, infiltrative ophthalmopathy.
Diagnosis
Diagnosis is suspected in infants whose mothers have Graves' disease and high titers of stimulatory antibodies (thyroid-stimulating immunoglobulins) and is confirmed by measuring free serum thyroxine (T4) and TSH. Diagnosis in adolescents is similar to that in adults and also includes thyroid function tests.
Treatment
Infants are given an antithyroid drug (eg, propylthiouracil 1.7 to 3.3 mg/kg po tid, methimazole 0.17 to 0.33 mg/kg po tid), sometimes with a β-blocker (eg, propranolol 0.8 mg/kg po tid) to treat symptoms. Treatment must be monitored closely and stopped as soon as the disease has run its course (for treatment of Graves' disease during pregnancy, see Pregnancy Complicated by Disease: Graves' disease). For older children and adolescents, treatment is similar to that for adults (see Thyroid Disorders: Treatment) and includes antithyroid drugs, radioactive sodium iodine, and sometimes surgery.
Last full review/revision May 2009 by Nicholas Jospe, MD
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