From the Guidelines
For hyperthyroidism evaluation, you should get thyroid function tests including TSH (thyroid stimulating hormone), free T4, and free T3, as these are the primary screening tests for thyroid dysfunction, according to the USPSTF recommendation statement 1.
Key Laboratory Tests
- TSH (thyroid stimulating hormone)
- Free T4
- Free T3 These tests are essential for diagnosing hyperthyroidism, as TSH will typically be suppressed while T4 and/or T3 will be elevated.
Additional Tests
Additional important tests include:
- Thyroid antibodies such as thyroid stimulating immunoglobulin (TSI) and thyroid peroxidase antibodies (TPO) to determine if Graves' disease is the cause
- A complete blood count (CBC) and comprehensive metabolic panel (CMP) to assess overall health status and rule out other conditions
- Thyroid ultrasound to identify nodules or gland enlargement
- A radioactive iodine uptake scan to determine the cause of hyperthyroidism by showing how actively the thyroid gland is absorbing iodine
- Thyroglobulin levels may be checked in some cases These tests collectively help diagnose the specific type of hyperthyroidism (Graves' disease, toxic nodular goiter, thyroiditis, etc.) which guides appropriate treatment.
Importance of Early Diagnosis
Early diagnosis is crucial as untreated hyperthyroidism can lead to serious complications, including heart problems and bone density loss. The USPSTF found no direct evidence that treatment of thyroid dysfunction based on risk level alters final health outcomes, but treatment is generally recommended for patients with a TSH level that is undetectable or less than 0.1 mIU/L, particularly those with overt Graves disease or nodular thyroid disease 1.
From the Research
Laboratory Tests for Diagnosing Hyperthyroidism
To diagnose hyperthyroidism, several laboratory tests are recommended, including:
- Biochemical tests, such as low TSH, high free thyroxine (FT4), or high free tri-iodothyonine (FT3) 2
- Measurement of serum hormone concentrations, such as TSH, FT4, and FT3 3
- Detection of serum autoantibodies against thyroid tissues, such as TgAb, TPOAb, and TSH receptor antibody 3
- Thyroid ultrasonography and scintigraphy to determine the underlying cause of hyperthyroidism 2
Specific Tests and Their Significance
- TSH measurement is considered the first choice in selecting the hormone determination, as it is the most reliable and informative regarding thyroid function 3
- FT4 measurement is preferred over total T4 (TT4) due to its ability to depict thyroid hormone levels within reference intervals, even in cases where TT4 is affected by changes in serum thyroid hormone binding proteins 3
- TSH receptor antibody measurement is essential in differentiating Graves' disease from other causes of hyperthyroidism 3, 4