Healthcare providers may conduct several additional tests to help confirm the diagnosis of hyperthyroidism, along with determining its cause and best treatment. These tests include:
- T3 and T4 test
- Thyroid-stimulating immunoglobulin (TSI) test
- Radioactive iodine uptake test
- Thyroid scan.
T3 and T4 Test
This test will show the levels of T3 and T4 in the blood. If a person has hyperthyroidism, the levels of one or both of these hormones in the blood will be higher than normal.
Thyroid-Stimulating Immunoglobulin Test
This test, also called a thyroid-stimulating antibody test, measures the level of TSI in the blood. Most people with Graves' disease (the most common cause of hyperthyroidism) have this antibody, but people whose hyperthyroidism is caused by something else do not.
Radioactive Iodine Uptake Test
The radioactive iodine uptake test measures the amount of iodine the thyroid collects from the bloodstream. Measuring the amount of iodine in the thyroid will help the healthcare provider know what is causing the overactive thyroid. For example, low levels of iodine uptake might be a sign of thyroiditis, whereas high levels could indicate Graves' disease.
A thyroid scan shows how and where iodine is distributed in the thyroid. This information helps the healthcare provider diagnose the cause of hyperthyroidism by providing images of nodules and other possible thyroid irregularities.