What do thyroid function tests include?

Thyroid function test is an important means to evaluate the health status of the thyroid gland, mainly includingHormone level testing(such as TSH, FT3, FT4),Antibody testing(e.g. TPOAb, TGAb) andImaging examination(such as ultrasound, nuclide scan). Among them, hormone testing is the core content, antibody testing assists in the diagnosis of autoimmune diseases, and imaging examinations are used to observe thyroid morphology and structure. The clinical significance and relevance of these examinations will be introduced in detail below.

1. Thyroid hormone testing
The core of thyroid function test isSerum hormone level measurement, mainly including:
1.Thyroid Stimulating Hormone (TSH): Secreted by the pituitary gland, it is a sensitive indicator for evaluating thyroid function. Abnormality indicates hyperthyroidism or hypothyroidism.
2.Free thyroxine (FT4): Reflects the actual secretion status of the thyroid gland and is not affected by binding proteins.
3.Free triiodothyronine (FT3): More active thyroid hormone, especially important in the diagnosis of hyperthyroidism.
These indicators need to be interpreted jointly. For example, reduced TSH combined with elevated FT4 may indicate primary hyperthyroidism.

2. Thyroid antibody test
When autoimmune thyroid disease is suspected,Antibody testing:
1.Thyroid peroxidase antibody (TPOAb): Highly related to Hashimoto's thyroiditis, with a positive rate of up to 90%.
2.Thyroglobulin Antibodies (TGAb): Common in autoimmune diseases and assists in the diagnosis of differentiated thyroid cancer.
3.TSH receptor antibodies (TRAb): It has specific diagnostic value for Graves' disease.
Antibody testing can help distinguish the cause. For example, TPOAb positivity coupled with elevated TSH indicates Hashimoto's thyroiditis.

3. Imaging and supplementary examinations
In addition to laboratory examinations,Imaging meansIndispensable:
1.Thyroid ultrasound: Evaluate the nature of the nodule (such as TI-RADS grade), gland size and blood flow.
2.radionuclide scan: Differentiate hot nodules from cold nodules, and assist in the diagnosis of Graves' disease.
3.Fine needle aspiration biopsy (FNA): Pathological diagnosis of suspected malignant nodules.
For example, when ultrasonography finds hypoechoic nodules with microcalcifications, FNA needs to be combined to determine benign and malignant.

Summary and clinical significance
Thyroid function test requiredMulti-dimensional comprehensive assessment: Hormone testing determines functional status, antibody testing identifies the cause, and imaging examinations locate lesions. For example, the typical manifestations of Graves' disease are reduced TSH, elevated FT4 with TRAb positivity, and diffuse thyroid enlargement. Commonly used clinical testing equipment includes Roche Cobas series, Abbott Architect, etc., but specific treatment plans need to be formulated by endocrinologists based on the test results.

Quote source:
1. "Internal Medicine" (9th edition), People's Medical Publishing House, edited by Wang Jiyao
2. American Thyroid Association (ATA) "Thyroid Function Testing Guidelines"
3. Testing equipment manufacturers: Roche Diagnostics (Cobas e601), Abbott Laboratories (Architect i2000)