Medications such as interferon and interleukin-2 (aldesleukin) also can cause type II. Type II is a thyroiditis that occurs in patients with normal thyroid glands. Amiodarone is the most common source of iodine excess in the United States. Because amiodarone contains 37 percent iodine, type I is an iodine-induced hyperthyroidism (see above). 5 Amiodarone-inducedĪmiodarone- (Cordarone-) induced hyperthyroidism can be found in up to 12 percent of treated patients, especially those in iodine-deficient areas, and occurs by two mechanisms. Excess iodine increases the synthesis and release of thyroid hormone in iodine-deficient patients and in older patients with preexisting multinodular goiters. Iodine-induced hyperthyroidism can occur after intake of excess iodine in the diet, exposure to radiographic contrast media, or medications. TREATMENT-INDUCED HYPERTHYRIODISM Iodine-induced (T 4= thyroxine T 3= triiodothyronine TSH = thyroidstimulating hormone.) Time course of changes in thyroid function tests in patients with thyroiditis. A transient hypothyroidism often occurs before resolution ( Figure 1 12). Postpartum thyroiditis can occur in up to 5 to 10 percent of women in the first three to six months after delivery. Lymphocytic thyroiditis and postpartum (subacute lymphocytic) thyroiditis are transient inflammatory causes of hyperthyroidism that, in the acute stage, may be clinically indistinguishable from Graves’ disease. This condition can be recurrent in some patients. Symptoms usually resolve within eight months. Subacute thyroiditis produces an abrupt onset of thyrotoxic symptoms as hormone leaks from an inflamed gland. Toxic adenomas are autonomously functioning nodules that are found most commonly in younger patients and in iodine-deficient areas. It typically occurs in patients older than 40 years with a long-standing goiter, and has a more insidious onset than Graves’ disease. Toxic multinodular goiter causes 5 percent of the cases of hyperthyroidism in the United States and can be 10 times more common in iodine-deficient areas. An infiltrative ophthalmopathy accompanies Graves’ disease in about 50 percent of patients. It can be familial and associated with other autoimmune diseases. 8 It is an autoimmune disease caused by an antibody, active against the thyroid-stimulating hormone (TSH) receptor, which stimulates the gland to synthesize and secrete excess thyroid hormone. Graves’ disease is the most common cause of hyperthyroidism, accounting for 60 to 80 percent of all cases. Iodine-induced hyperfunctioning of thyroid gland (iodide ingestion, radiographic contrast, amiodarone )įunctioning pituitary adenoma (thyroid-stimulating hormone) trophoplastic tumors (human chorionic gonadotropin) Increased glandular stimulation (substance causing stimulation) Graves’ disease (thyroid-stimulating antibody) Lymphocytic thyroiditis, postpartum thyroiditis, medication-induced thyroiditis TABLE 2 Common Etiology and Clinical Diagnosis of Hyperthyroidism Cause 1 As many as 15 percent of cases of hyperthyroidism occur in patients older than 60 years. The prevalence of hyperthyroidism in community-based studies has been estimated at 2 percent for women and 0.2 percent for men. Etiologic diagnosis influences prognosis and therapy. Patients’ desires must be considered when deciding on appropriate therapy, and close monitoring is essential.Ĭlinical hyperthyroidism, also called thyrotoxicosis, is caused by the effects of excess thyroid hormone and can be triggered by different disorders. Special treatment consideration must be given to patients who are pregnant or breastfeeding, as well as those with Graves’ ophthalmopathy or amiodarone-induced hyperthyroidism. Some new therapies are under investigation. Thyroidectomy is an option when other treatments fail or are contraindicated, or when a goiter is causing compressive symptoms. Graves’ disease, toxic multinodular goiter, and toxic adenoma can be treated with radioactive iodine, antithyroid drugs, or surgery, but in the United States, radioactive iodine is the treatment of choice in patients without contraindications. When thyroiditis is the cause, symptomatic treatment usually is sufficient because the associated hyperthyroidism is transient. When test results are uncertain, measuring radionuclide uptake helps distinguish among possible causes. The diagnostic workup begins with a thyroid-stimulating hormone level test. Other common causes include thyroiditis, toxic multinodular goiter, toxic adenomas, and side effects of certain medications. The most common cause of hyperthyroidism is Graves’ disease. The proper treatment of hyperthyroidism depends on recognition of the signs and symptoms of the disease and determination of the etiology.