From the Research
Introduction to Suppressed Thyroid-Stimulating Hormone (TSH)
Suppressed TSH levels can indicate hyperthyroidism or other thyroid disorders. To accurately diagnose and manage these conditions, additional lab tests are necessary.
Additional Lab Tests for Suppressed TSH
The following tests can help diagnose the underlying cause of suppressed TSH:
- Free thyroxine (FT4) level: This test measures the level of thyroxine in the blood, which can help differentiate between hyperthyroidism and other conditions 1.
- Free triiodothyronine (FT3) level: This test measures the level of triiodothyronine in the blood, which can help diagnose hyperthyroidism 1.
- Thyroid hormone autoantibodies: These tests can help diagnose autoimmune thyroid disorders, such as Graves' disease 2.
- Thyroid-stimulating immunoglobulins: These tests can help diagnose Graves' disease, a common cause of hyperthyroidism.
Interferences with Thyroid Function Tests
Certain substances and conditions can interfere with thyroid function tests, including:
- Biotin: High levels of biotin can interfere with TSH and FT4 tests 2.
- Anti-ruthenium antibodies: These antibodies can interfere with TSH and FT4 tests 2.
- Heterophilic antibodies: These antibodies can interfere with TSH and FT4 tests 2, 3.
Clinical Implications and Detection Algorithm
A detection algorithm can help identify interferences with thyroid function tests, including:
- Assay method comparison: Comparing results from different assay methods can help identify interferences 2.
- Dilution procedures: Diluting samples can help identify interferences caused by high levels of certain substances 2.
- Blocking reagents studies: Using blocking reagents can help identify interferences caused by certain antibodies 2.
- Polyethylene glycol precipitation: This method can help identify interferences caused by certain substances 2.
Treatment and Management
Treatment and management of suppressed TSH depend on the underlying cause. For example:
- Hyperthyroidism: Treatment may involve anti-thyroid medications, radioactive iodine, or surgery.
- Thyroid hormone replacement therapy: This treatment may involve taking synthetic thyroid hormones to replace deficient hormones.
Caveats and Differentials
When interpreting TSH results, it is essential to consider the following:
- Non-thyroidal illness: Certain illnesses can affect TSH levels, making it essential to interpret results cautiously 4.
- Pregnancy: TSH levels can be affected by pregnancy, making it essential to use pregnancy-specific reference ranges 1.
- Age: TSH levels can be affected by age, making it essential to use age-specific reference ranges 1.