Hyperthyroidism: Diagnosis and Treatment

Diagnosis

TSH is the most cost–effective assay for hyperthyroidism and should be the initial screening test. TSH is decreased in primary hyperthyroidism. Elevated (or sometimes normal) TSH levels alongside elevated thyroxine (T4) or triiodothyronine (T3) levels suggest secondary hyperthyroidism.

Free T4 concentration is increased; the magnitude of T4 elevation is correlated with the degree of biochemical disease.

Once hyperthyroidism has been diagnosed, further testing can determine the underlying etiology. Antithyroglobulin and antithyroid peroxidase antibodies may be present in Graves’ disease. A 24–hour radioactive iodine uptake scan is often necessary for diagnosis of Graves’ disease and exclusion of other disorders. Uptake is increased in Graves’ disease, toxic adenoma, and multinodular goiter, and is decreased in thyroiditis, excessive iodine consumption, and overmedication with thyroid hormone supplementation.

Radioimaging can define the shape and size of the thyroid and determine where “hot” nodules are distributed (iodine will concentrate in “hot” nodules). Functional nodules may represent toxic adenoma or multinodular goiter. Diffuse uptake is seen in Graves’ disease.

Treatment

Initial therapy often uses a beta–blocker to oppose the adrenergic effects of thyroid hormone.

Antithyroid drugs (eg, propylthiouracil, methimazole) interfere with thyroid hormone production. Although antithyroid drugs must generally be continued for at least 1 to 2 years, they may be a useful temporizing measure in anticipation of spontaneous remission of hyperthyroidism.

Radioactive iodine (I131) to ablate thyroid tissue is a definitive treatment with excellent success rates; it is the most commonly used treatment. It cannot, however, be used in pregnancy.

Surgical removal of the thyroid (thyroidectomy) is also an effective treatment. It is often indicated in hyperthyroid patients who have an obstructive goiter.
Lifelong thyroid hormone supplementation will be necessary after ablation or thyroidectomy due to resultant hypothyroidism.

Thyroid storm treatment is generally similar to that for hyperthyroidism, but with closer monitoring and higher medication doses. Treatment with glucocorticoids or potassium iodine may be indicated. Intensive care unit observation is essential.