Diagnosis of Hyperthyroidism

Your physician will first perform a physical examination to check for any obvious symptoms of hyperthyroidism. In addition, other diagnostic studies include the following:

• Blood Tests: Blood tests are performed that measure the levels of the thyroid hormones, T4 and T3, which must be high to make a diagnosis of hyperthyroidism. The level of thyroid stimulating hormone (TSH) also is measured. With hyperthyroidism TSH is low while T4 and T3 levels are high.

• Iodine Uptake Scan: This test measures thyroid function by determining how much iodine is taken up by the thyroid gland. Patients are given a small dose of radioactive iodine that is taken on an empty stomach. The iodine is concentrated in the thyroid gland or excreted in the urine over the next few hours. The amount of iodine that goes into the thyroid gland is then measured.

• Thyroid Scan: This test typically is performed at the same time as the iodine uptake test because it also requires that a patient take radioactive iodine, which then concentrates in the thyroid gland. Thyroid scans use the emissions of gamma rays from radioactive iodine to obtain a picture of the thyroid.