Thyroid tests are performed on blood samples collected in a medical facility, according to the National Endocrine and Metabolic Diseases Information Service. Tests ordered may include TSH, or thyroid-stimulating hormone tests, tests to check T4 and T3 levels, thyroid-stimulating immunoglobulin tests and antithyroid antibody tests.
The TSH test is the most common thyroid test, notes the National Endocrine and Metabolic Diseases Information Service. This test measures the amount of TSH being secreted by the thyroid gland and can be useful in diagnosing both hypothyroidism and hyperthyroidism. Healthcare professionals may also order imaging tests of the thyroid, such as ultrasounds and CT scans if abnormalities are detected.