total thyroxine

3,5,3',5' tetraiodothyronine, Thyroxine (T4), is the most secreted hormone in the thyroid. Its concentration in the blood is 30 to 60 times higher than that of T3. It is T3. The main source. Under normal conditions, T4 binds primarily to thyroid hormone binding globulin (TBG). The TT4 assay is one of the basic in vitro experiments on thyroid function status. Basic Information Specialist classification: growth and development examination classification: blood examination Applicable gender: whether men and women apply fasting: fasting Analysis results: Below normal: 1. Glucocorticoids can lower the levels of TSH and thyroid-binding globulin (TBG) in the blood. Therefore, serum and TT4 may be decreased in various cases of hypercortisolism. 2. Subacute thyroiditis and chronic lymphocytic thyroiditis in the late stage due to excessive destruction of follicles, thyroid hormone synthesis and release decreased, TT4 levels can be reduced. 3. The concentration of thyroid hormone-binding globulin (TBG) in blood is an important factor affecting the level of TT4. The concentration of TT4 in patients with low TBG is correspondingly reduced. Normal value: Total thyroxine: 65-156nmol/L Above normal: 1. TT4 was significantly elevated in hyperthyroidism, and TT4 concentration was elevated in patients with T4 hyperthyroidism. 2. Patients with hypothyroidism decreased significantly; peripheral hypothyroidism due to defects in thyroid hormone receptors or receptors, resulting in peripheral tissue is not sensitive to T4, T4 compensatory secretion increased. Patients with high TBGemia have elevated TT4 concentrations. negative: Positive: Tips: Actively cooperate with doctors. Normal value 65 to 156 nmol/L. Clinical significance (1) Glucocorticoids can lower the levels of TSH and thyroid-binding globulin (TBG) in the blood. Therefore, serum and TT4 may be decreased in various cases of hypercortisolism. (2) TT4 increased significantly in hyperthyroidism, T4 type hyperthyroidism patients increased TT4 concentration, while TT3 concentration was normal. Patients with hypothyroidism were significantly reduced; peripheral hypothyroidism due to defects in the thyroid hormone receptor or receptor, resulting in peripheral tissue is not sensitive to T4, T4 compensatory secretion increased. (3) Subacute thyroiditis and chronic lymphocytic thyroiditis In the early stage, due to thyroid follicular destruction, thyroid hormone release increased, TT4 increased, and later, due to excessive destruction of follicles, thyroid hormone synthesis and release decreased, TT4 The level can be lowered. (4) The concentration of thyroid hormone-binding globulin (TBG) in blood is an important factor affecting the level of TT4. In patients with high TBG, the concentration of TT4 is elevated. Conversely, the concentration of TT4 in patients with low TBG is correspondingly reduced. (5) A variety of drugs can affect the level of TT4 through different links, such as iodine-containing drugs, estrogens, contraceptives, beta-blockers, etc. In the determination of thyroid hormones, attention should be taken to eliminate interference. Low results may be diseases: high incidence of hyperthyroidism in the elderly may be diseases: pregnancy with hyperthyroidism, pregnancy with hyperthyroidism, Graves disease, hyperthyroidism in the elderly, nodular goiter in children, pregnancy with increased cortisol Symptoms, hyperthyroidism, hyperthyroidism during pregnancy (1) The sensitivity of the measurement was 5.1 nmol/L, and the non-specific binding rate (NSB) was less than 10%; the measurement range was 0 to 309 nmol/L (0 to 240 μg/L). (2) Anti-T4 serum does not cross-react with monoiodotyrosine, diiodotyrosine, and triiodothyronine, so this assay is specific for T4. (3) Before shaking, it must be shaken well to ensure the matrix is ​​uniform. The incubation temperature can be from 20 to 36 °C. If the room temperature is lower than 20 °C, it should be incubated with an incubator. (4) Shake well before centrifugation. (5) All reagents in the kit must be stored at 2 to 4 °C. The serum to be tested should be stored in the refrigerator. If it is more than 3 days, it should be packed into several small bottles and stored at -20 °C. The measurement results will not be affected within 1 month. (6) The highest binding rate of the antiserum of the kit can be used from 35% to 65%. The calculation method subtracts the NSB tube count from the standard tube sedimentation count, divided by the total T count minus the instrument background. (7) Some serum or biological fluids with known T4 content can be stored in the laboratory and used as quality control for each measurement. It is best to have low, medium and high concentrations. (8) The measurement is often affected by the iodine-containing diet, the drug, and the concentration of TBG. Inspection process TT4 radioimmunoassay. Not suitable for the crowd Generally no taboos. A variety of drugs can affect the level of TT4 through different links, such as iodine-containing drugs, estrogen, contraceptives, beta blockers, etc., in the determination of thyroid hormones, should be noted to exclude interference. The person being tested should stop taking it immediately before taking the test. Adverse reactions and risks Generally not.

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