- Thyrotoxicosis is a hypermetabolic clinical state of thyroid hormone excess either caused by overproduction of thyroid hormone by the thyroid gland or by administration of exogenous synthetic hormone.
- The most common disorder causing thyrotoxicosis in children is Graves' disease.
- Thyroid hormones upregulate β-adrenergic receptors causing symptoms of sympathetic nervous system overactivity.
- Signs of sympathetic hyperactivity include tremor, brisk deep tendon reflexes, tachycardia, supraventricular tachycardia, flow murmur, overactive precordium, and a widened pulse pressure. Other cardiac disturbances such as atrial fibrillation and congestive heart failure (CHF) may also occur.
- Precipitating factors for thyroid storm in a patient with hyperthyroidism are thyroid surgery, withdrawal of antithyroid medications, radioiodine therapy, palpation of a goiter, iodinated contrast dyes, and stress.
- Physical findings in Graves' disease, such as eye signs, are usually subtle in children.
- Thyroid storm is suggested by severe hyperpyrexia, atrial dysrhythmia, CHF, delirium or psychosis, severe gastrointestinal hyperactivity, and hepatic dysfunction with jaundice.
- Treatment consists of antithyroid drugs propylthiouracil (PTU) at a dosage of 175 mg/m2/d or 4 to 6 mg/kg/d at 6- or 8-hour intervals, iodine therapy started 1 hour after antithyroid medication is initiated, β-adrenergic blockade with propranolol, 10 to 20 mg every 12 to 8 hours, and supportive management.
Hyperthyroidism is a state of increased production and secretion of thyroid hormones resulting in the hypermetabolic clinical syndrome of thyrotoxicosis. The term thyroid storm refers to an extreme state of decompensated thyrotoxicosis and is a thyroid emergency that can be potentially fatal.
The most common cause of hyperthyroidism in children is Graves' disease. This disease occurs in 1 in 5000 children with a peak incidence between 11 and 15 years of age. The male to female ratio is 1:5.1 Although the true incidence of childhood thyrotoxicosis is unknown, 5% of all thyrotoxicosis occurs in childhood2 and 0.6% to 10% of neonates born to mothers with Graves' disease will show signs of thyrotoxicosis.3 The reported mortality in neonatal thyrotoxicosis is as high as 20%.4 Because childhood hyperthyroidism occurs mostly in adolescents, thyroid storm also occurs more frequently in this group.2 (Figure 78–1).
Etiology and pathophysiology of thyrotoxicosis and thyroid storm.
Thyrotoxicosis results from thyroid hormone excess either caused by overproduction of thyroid hormone by the thyroid gland or by administration of synthetic hormone. Increased concentration of serum free thyroid hormone is almost always found in thyrotoxicosis. In Graves' disease, activated B-lymphocytes produce antibodies against antigen shared by the thyroid gland and eye muscle.1,5 Thyrotropin receptor-stimulating antibodies (TRSAb) bind to TSH receptors to increase thyroid hormone production. In congenital hyperthyroidism, transplacental transfer of TRSAb from the mother with Graves' disease stimulates the thyroid gland to cause hyperthyroidism or thyrotoxicoxis.1,3,4
The actions of thyroid hormone at the cellular level include calorigenesis, acceleration of ...