What does a full thyroid test mainly check?

Total triiodothyronine (TT3)

Normal reference value: 0.45～1.37 ng/ml

TT3 is the main hormone of thyroid hormone on various target organs. The serum TT3 concentration reflects the function of the thyroid gland on peripheral tissues better than the secretion status of the thyroid gland. TT3 is an important indicator for identifying early hyperthyroidism and monitoring recurrent hyperthyroidism. TT3 measurement can also be used to identify T3 type hyperthyroidism and diagnose pseudothyrotoxicosis.

Total thyroxine (TT4)

Normal reference value: 4.5～12 ug/dl

TT4 is the main product of thyroid secretion and an indispensable component of the integrity of the hypothalamus-anterior pituitary-thyroid regulatory system. TT4 measurement can be used for the diagnosis of hyperthyroidism, primary and secondary hypothyroidism, and monitoring of TSH suppression therapy.

Free triiodothyronine (FT3) / Free thyroxine (FT4)

Normal reference values: FT3 1.45～3.48 pg/ml FT4 0.71～1.85 ng/dl

FT3 content is of great significance in distinguishing whether the thyroid function is normal, hyperthyroid or hypothyroid. It is very sensitive to the diagnosis of hyperthyroidism and is a specific indicator for diagnosing T3 hyperthyroidism.

FT4 measurement is an important part of routine clinical diagnosis and can be used as a means of monitoring thyroid suppression therapy. FT4 and TSH are often measured together when thyroid dysfunction is suspected.

Thyroid stimulating hormone (TSH)

Normal reference value: 0.49～4.67 mIU/L

TSH testing is a preliminary screening test for thyroid function. A small change in the free thyroid concentration will result in a significant adjustment in the TSH concentration in the opposite direction. Therefore, TSH is a very sensitive and specific parameter for testing thyroid function, and is particularly suitable for early detection or exclusion of functional disorders in the hypothalamus-pituitary-thyroid central regulatory circuit.

Anti-thyroid globulin antibody (Anti-TG, TGA)

Normal reference value: 0～34 IU/ml

Thyroglobulin (TBG) is a potential autoantigen that can stimulate the body to produce TGA when it enters the blood. TGA is the first autoantibody discovered in thyroid disease. It is highly species-specific and is a common indicator for diagnosing autoimmune thyroid disease (AITD).