Childhood Hyperthyroidism

Hyperthyroidism occurs much less commonly in children than hypothyroidism, yet is a far more virulent condition [7, 8]. In children the most common cause of childhood thyrotoxicosis is Graves' disease, which is characterized by diffuse goiter, hyperthyroidism and occasionally ophthalmopathy [6, 9-11]. Other causes of childhood hyperthyroidism include toxic nodules, toxic multinodular goiters, acute and subacute thyroiditis, and the ingestion of thyroid hormone [6, 9-11].

Untreated, hyperthyroidism is associated with excessive activity, tremor, tachycardia, flushing, palpitations, accelerated linear growth, weight loss, impaired skeletal mineralization, and poor school performance [6, 9-11]. Because Graves' disease, toxic nodules and toxic multinodular goiters only rarely spontaneously resolve within a short period, treatment of hyper-thyroidism is essential. Current treatment options include the use of radioactive iodine, surgery, and antithyroid medications.

Central to considering the use of radioactive iodine and other treatment options in Graves disease in the pediatric population, is recognition of the natural history of the autoimmune disorder. One must also consider how long antithyroid drug therapy should be continued before moving on to definitive therapy.

Spontaneous remission of Graves' disease in the pediatric population occurs in the minority of individuals. Published remission rates are usually less than 25% after several years of antithyroid therapy [5, 6, 12]. The most extensive long-term study of this issue involving nearly 200 children showed that less than 20% of children treated medically achieved remission lasting greater than 2 years [13]. In another large series of 186 children, less than 30% of children went into remission [14]. When responses to medical therapy between prepu-bertal and pubertal children are compared, remission rates are even less in pre-pubertal than pubertal children, with remission occurring in fewer than 15% of prepubescent children [15, 16].

When spontaneous remission of Graves' disease does not occur, prolonged drug therapy will control the hyperthyroid state and is used by some clinicians; however, years of treatment with antithyroid drugs do not appear to increase the likelihood of lasting remission. More than two decades ago, Greer et al. [17] showed that the likelihood of spontaneous remission of hyperthyroidism was similar when antithyroid medications were used for 6 or 36 months. Most recently, Weetman [18] reviewed prospective trials comparing different durations of treatment in adult subjects. In one French study involving 94 patients, following treatment for 6 or 18 months, remission rates were 42 and 62%, respectively, 2 years after discontinuing treatment [19]. In 52 Spanish patients, following treatment for 12 or 24 months, remission rates were 46 and 54% at 2 years after cessation of therapy [20]. This difference was not significant, and by 5 years, the relapse rate was 85%. Another study of 134 French patients found no benefit of 18 vs. 43 months of treatment [21]. It is notable that remission rates in these cohorts of adults are considerably greater than those reported in children, suggesting that the younger one is when Graves' disease occurs, the more lasting it will be.

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