Hyperthyroidism in children

Hyperthyroidism refers to over activity of the thyroid gland, which leads to excessive release of thyroid hormones and consequently accelerated metabolism in the peripheral tissues. Thyrotoxicosis, however, refers to the clinical effects of unbound thyroid hormones, whether or not the thyroid gland is the primary source.

Hyperthyroidism is a relatively rare condition in children. The vast majority of cases are caused by Graves disease. Numerous therapeutic options are available, so most patients do well. The risk of relapse or subsequent hypothyroidism is substantially higher in adults than in children and adolescents.

Hyperthyroidism in childhood include the following:

- Graves disease

- Toxic adenoma, toxic nodular goiter

- McCune-Albright syndrome

- Sub-acute (viral) thyroiditis

- Chronic lymphocytic thyroiditis

- Bacterial thyroiditis

Pituitary causes of thyrotoxicosis in childhood include pituitary adenoma and pituitary resistance to T4. Other causes of thyrotoxicosis in childhood include the following:

- Exogenous thyroid hormone

- Iodine-induced hyperthyroidism (Jod-Basedow phenomenon)

- Human chorionic gonadotropin (hCG) secreting tumor

Graves disease is associated with human leukocyte antigen (HLA)-B8 and HLA-DR3 and is more common in some families than in others. Although females are affected by Graves disease more often than males, with a reported female-to-male ratio of 3-6:1, the frequency of neonatal Graves disease is equal in males and females.

The course of neonatal Graves disease is self-limiting, the prognosis is considerably worse than that in older children. As a result of their disease, patients are prone to prematurity, airway obstruction, and heart failure. The mortality rate from these conditions has been as high as 16%. Complications from hyperthyroidism include the following:

- Congestive heart failure

- Craniosynostosis in neonates

- Developmental delay in neonates

- Hypothyroidism

Remission rates of Graves disease vary from 34-64% in patients taking antithyroid medication. Recurrence can occur months or years after the discontinuation of therapy. Treatment with radioiodine or surgical subthyroidectomy is very effective, but most patients develop hypothyroidism and require lifelong thyroid replacement.

The common symptoms of hyperactivity, nervousness and emotional lability are often attributed to other causes, most frequently attention deficit hyperactivity disorder (ADHD). Alterations in mental status may be seen in almost one half of all patients with thyroid dysfunction. Deterioration of behavior and school performance in a child who previously did well may be the earliest warning signal. Other symptoms of Graves disease can include weight loss despite excellent appetite, sweating,  hyperactivity, heat intolerance, palpitations, fatigue and muscle weakness etc.

Patients with Graves disease present with diffuse, nontender and symmetric enlargement of the thyroid gland. Goiter is rarely the presenting complaint, but it is invariably present (99%); absence of a goiter makes the diagnosis of Graves disease subject to question. Cardiac examination may reveal tachycardia and wide pulse pressure or hypertension. Patients may have a wide variety of eye findings like exophthalmos, lid lag, lid retraction, chemosis, periorbital oedema, optic atrophy etc. Other physical findings may include smooth sweaty skin, tremor or muscle fasciculation, proximal muscle weakness, systemic hypertension etc.

Thyroid Function Tests

Hyperthyroidism can be confirmed simply and quickly with measurements of T4, T3, T3 resin uptake (T3RU), and thyroid-stimulating hormone (TSH). Patients with Graves disease have elevated levels of T4, T3, and T3 RU and low or undetectable levels of TSH.

Treatment

Surgery is the oldest treatment for Graves disease and is quite effective. Generally, patients are initially treated with antithyroid medications. Iodide is then added before surgery to decrease the vascularity of the thyroid gland. To minimize risk of recurrence, most of the gland is removed. Consequently, the risk of permanent hypothyroidism is high. Patients may require lifelong T4 replacement. Overall, treatment with antithyroid medications is a relatively safe option, provided that patients are willing to participate in prolonged therapy. Currently, this is considered to be the treatment of choice in children and adolescents.

The writer is an Endocrinologist. E-mail: selimshahjada@gmail.com