This is a specialized blood test that evaluates the amount of thyroid hormones in the blood. It screens for Free T3 (tri-iodothyronine), Free T4 (tetra-iodothyronine) and TSH (thyroid stimulating hormone). The test is carried out for
Free T4 and TSH levels help in confirming the diagnosis of hypothyroidism as well as hyperthyroidism but Free T3 levels only help in testing for hyperthyroidism or assessing its severity.
This test is performed when a patient has
The test result is normal; if levels of Free T3 are 3.5-7.8 pmol/L, levels of Free T4 9.0-25.0 pmol/L and TSH levels are 0.5-5.0 mU/L. It means
If TSH levels are > 10 mU/L (high) and Free T4 levels are <5.0 pmol/L (low); it indicates
If TSH levels are < 0.5 mU/L (low) and Free T4 levels are > 25.0 pmol/L (high); it indicates
If TSH levels are > 5 mU/L but < 10 mU/L and Free T4 levels are 9.0-25.0 pmol/L; it means
If TSH levels are < 0.5 mU/L (low) and Free T4 levels are < 9 pmol/L (low); it means
If Free T3 levels are > 8 pmol/L (high), it means
If Free T3 levels are very high, it means severe form of hyperthyroidism.