1.Total triiodothyronine (TT3 )
TT3 is the main hormone for the action of thyroid hormone on various target organs. The serum TT3 concentration reflects the function of the thyroid gland on peripheral tissues better than the secretory status of the thyroid gland. TT3 is an important indicator for identifying early hyperthyroidism and monitoring recurrent hyperthyroidism. TT3 measurement can also be used for the identification of T3 hyperthyroidism and the diagnosis of pseudo-thyrotoxicosis.
Increased: hyperthyroidism, hyperTBGemia, medically induced hyperthyroidism, TT3 is relatively increased during hyperthyroidism treatment and early hypothyroidism; TT4 may be decreased in patients with iodine deficiency goiter, but TT3 is normal and also relatively increased; T3 hyperthyroidism, some hyperthyroid patients have normal TT4 concentration, TSH is decreased and TT3 is significantly increased. Decrease: hypothyroidism, low T3 syndrome (seen in various serious infections, chronic heart, kidney, liver and lung failure, chronic wasting disease, etc.), low TBGemia, etc.
Normal reference value: 0.45~1.37 ng/ml
2.Total thyroxine (TT4)
TT4 is the main product of thyroid secretion and an indispensable component of the integrity of the hypothalamic-pituitary-thyroid regulatory system. TT4 measurement can be used for the diagnosis of hyperthyroidism, primary and secondary hypothyroidism, and the monitoring of TSH suppression therapy.
Increased: hyperthyroidism, hyperTBGemia (pregnancy, oral estrogen and oral contraceptives, familial), acute thyroiditis, subacute thyroiditis, acute hepatitis, obesity, thyroid hormone application, consumption of thyroid tissue rich in thyroid hormones, etc.
Decrease: Hypothyroidism, hypotremia (nephrotic syndrome, chronic liver disease, protein-losing enteropathy, hereditary hypotremia, etc.), total hypopituitarism, hypothalamus “Yeol’s vigorous activity, etc.
Normal reference value: 4.5~12 ug/dl
3.Free triiodothyronine (FT3) / Free thyroxine (FT4)
FT3 and FT4 are the physiologically active forms of T3 and T4 and are a true reflection of the metabolic state of the thyroid gland. FT3 and FT4 are more sensitive and meaningful than T3 and T4. FT3 and FT4 have the advantage of not being affected by changes in their binding protein concentrations and binding characteristics, so there is no need to measure binding parameters separately.
FT3 level is important for differential diagnosis of normal, hyper or hypothyroidism, and is sensitive for the diagnosis of hyperthyroidism, and is a specific indicator for the diagnosis of T3 hyperthyroidism.
FT4 measurement is an important part of routine clinical diagnosis and can be used as a monitoring tool for thyroid suppression therapy. When thyroid dysfunction is suspected, FT4 and TSH are often measured together.
The triple test of TSH, FT3 and FT4 is commonly used to confirm hyperthyroidism or hypothyroidism, as well as to track the effectiveness of treatment.
Normal reference values: FT3 1.45-3.48 pg/ml FT4 0.71-1.85 ng/dl
4.Thyroid stimulating hormone (TSH)
TSH test is a primary screening test to identify thyroid function. A micro “xay in the free thyroid concentration brings about 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 dysfunction of the central hypothalamic-pituitary-thyroid regulatory loop.
Serum TSH is elevated in patients with TSH-secreting pituitary tumors, and TSH is an important indicator for monitoring thyroid cancer after surgery or after radiation therapy using thyroxine suppressive therapy.
Increased: primary hypothyroidism, ectopic TSH secretory syndrome (ectopic TSH tumor), pituitary TSH tumor, recovery from subacute thyroiditis. Decreased: Secondary hypothyroidism, tertiary (hypothalamic) hypothyroidism, with the exception of those due to hyperthyroidism CTSH tumor, and low measured values in those with EDTA anticoagulation.
Normal reference value: 0.49~4.67 mIU/L
5.Anti-Thyroglobulin antibody (Anti-TG, TGA)
Thyroglobulin (TBG) is a potential auto-antigen that stimulates the body to produce TGA when it enters the bloodstream, which is the first auto-antibody found in thyroid disease and is highly species-specific and a common indicator for diagnosing autoimmune thyroid disease (AITD).
Elevated TGA concentrations can be found in patients with autoimmune thyroiditis and occur about 70-80% of the time. 60% of Graves’ disease is positive for TGA, and a decrease in titer after treatment indicates effective treatment. A positive TGA with high titer in hyperthyroidism indicates that anti-thyroid medication is ineffective and prone to recurrence after stopping medication. There is a correlation between thyroid cancer and TGA, with a positive rate of 13%-65%. An elevated TGA value is a sign of tumor deterioration.
Normal reference value: 0-34 IU/ml
6.Anti-Thyroid microsomal antibody (Anti-TM, TMA)
TMA is one of the autoantibodies caused by autoimmune thyroid disease. It is recognized as an important marker of the autoimmune process of the thyroid gland, as well as TGA, and is the most representative antibody, which is an indispensable indicator for the diagnosis of autoimmune thyroid disease.
In autoimmune thyroiditis (i.e. Graves’ disease), serum TGA and TMA are significantly higher than in normal subjects and other non-autoimmune thyroid diseases, and are of great value in the differential diagnosis of autoimmune thyroiditis, with a diagnostic compliance rate of up to 98% when the two are combined.
Serum TMA and TGA are significantly higher than normal in patients with immune diseases such as Hashimoto’s thyroiditis, primary hypothyroidism and hyperthyroidism, especially in Hashimoto’s thyroiditis, and serum TMA and TGA are “specific indicators” for the diagnosis of these diseases.
Both TMA and TGA are “specific indicators” for the diagnosis of these diseases. ① Hyperthyroidism: TGA and TMA are strongly positive, TMA is higher than TGA, and both antibodies are lower than Hashimoto’s thyroiditis. Some patients may turn negative for TGA and TMA after treatment, but most clinically cured patients with hyperthyroidism have weakly positive TGA and TMA for a long time. Therefore, thyroid function should be rechecked regularly to prevent recurrence.
Hashimoto’s thyroiditis and Addison’s disease: TGA and TMA are both strongly positive, while some patients are strongly positive for TMA and weakly positive or negative for TGA. The two antibodies are significantly higher than normal in patients with subthyroiditis and lower than in Hashimoto’s thyroiditis.
③ Primary hypothyroidism: TGA and TMA are positive, but secondary hypothyroidism TGA and TMA are negative, to identify secondary hypothyroidism.
④ Thyroid cancer: TGA is increased significantly.
⑤ Autoimmune disease during pregnancy: TGA and TMA can be increased.
Normal reference value: 0~50 IU / ml
7.Anti-Thyroid peroxidase antibody (Anti-TPO, TPOA)
TPOA is the main thyroid tissue autoantibody, which is a key enzyme in the synthesis process of thyroid hormone and is closely related to immune damage of thyroid tissue. They mainly include thyroid-stimulating antibodies (TS-Ab) and thyroid-stimulating-blocking antibodies (TSB-Ab).
TPOA directly counteracts thyroid peroxidase (TPO), which catalyzes the iodination of thyroglobulin tyrosine during the biosynthesis of T3 and T4. Recent studies have confirmed that TPO is the main component of thyroid microsomal antigens and that TPOA is the active component of TMA, so the TPOA present in the patient is TMA.
TPOA is closely related to the occurrence and development of autoimmune thyroid disease (A ITD), and can cause autoimmune-related hypothyroidism through cell-mediated and antibody-dependent cytotoxic effects on thyroid hormone secretion. As a diagnostic and monitoring indicator of autoimmune thyroid disease, TPA has better sensitivity, specificity, reliability and significance than TMA, and has become the preferred indicator for the diagnosis of thyroid disease.
The main clinical applications of TPOA are: diagnosis of Hashimoto’s disease (HD) and autoimmune hyperthyroidism; toxicity of diffuse goiter (Graves); monitoring the effect of immunotherapy; detecting the possible development of familial thyroid disease; predicting the occurrence of postpartum thyroid dysfunction in pregnant women.
In patients with primary hypothyroidism, in combination with elevated TSH, early hypothyroid patients can be detected. In patients with suspected hypothyroidism, if TPOA is elevated, it can help to differentiate primary and secondary hypothyroidism. in patients with HT, TPOA is present throughout life, and if the clinical manifestations are typical and TPOA is persistently high, it can be used as a diagnostic basis to confirm the diagnosis.