Total triiodothyronine (T3)
【Reference value】1.8-2.9 nM/L (nmoML)
Clinical significance
1.Increases.
(1), in hyperthyroidism are increased, especially than T4 increased significantly, often higher than normal 4 times.
(2) Increased only in T3 hyperthyroidism, which is common in iodine-deficient areas, and also in highly functional thyroid adenomas, multinodular goiter, and when treated with thyroxine tablets for hyperthyroidism and hypothyroidism. Bay Kangli, Department of Gastroenterology, Xi’an Children’s Hospital
(3) T3 may be increased in early hyperthyroidism or in the early stage of recurrence
(4) Pregnancy, hepatitis, hyperthyroglobulinemia, or the use of contraceptives and estrogen can also cause T3 and T4 to increase, but to a lesser extent.
2. Decrease.
(1), nephrotic syndrome, hypoproteinemia, etc., can lower T3.
(2), the use of β-blockers, hormones, phenytoin sodium (dalantin), sulfopiridone (benzosulfone) and other drugs, T3 can also be reduced
(3), hypothyroidism, but the diagnosis of hypothyroidism is not as valuable as T4 reduction.
(4), cirrhosis of the liver, early heart attack, poor control of diabetes, T3 is reduced
(5), T3 can also be lowered by starvation, etc.
Total thyroxine (T4)
[Reference value] Radioimmunoassay: normal adults: 65-156 nmol/L (nmolML); Immunochemiluminescence: normal adults: 58.1-154.8 nmol/L (nmolML)
【Clinical significance】.
1. Increased.
(1), T4 type hyperthyroidism. Excessive intake of iodine-containing foods
(2), Pseudo T4 hyperthyroidism. Seen in myocardial infarction, pulmonary heart disease, acute cerebrovascular disease, asthma, tumor, acute liver disease, etc. It can be reduced with the improvement of the primary disease.
(3). Subacute thyroiditis.
(4). May suggest hyperthyroidism, but early or mild hyperthyroidism is not as obvious as elevation.
(5) A small number of elderly people with hyperthyroidism.
2. Decreased.
(1), Diagnosis of hypothyroidism is more sensitive than T3.
(2) In iodine-deficient goiter, T4 is reduced, T3 is normal, and TSH is elevated.
(3), Application of glucocorticoids, estrogen, salicylic acid and other drugs and in the treatment of hyperthyroidism.
(4). Decreased T4 in critically ill patients, suggesting poor prognosis.
Free triiodothyronine (FT3) and free thyroxine (FT4)
Reference values] FT3: 2.16-6.78 picomoles per liter (pmmolML); FT4: 1.03-6.78 picomoles per liter (pmmolML)
[Clinical significance].
If multiple indicators are evaluated comprehensively, the diagnostic value of hyperthyroidism is FT3 > FT4 = TSH > T3 > T4. The diagnostic value of hypothyroidism is: = TSH > T4 > FT3 > T3.
Thyroid stimulating hormone (TSH)
[Reference value] 2-10 milliunits/liter (muML).
【Clinical significance】.
TSH is an important indicator for the diagnosis of primary and secondary hypothyroidism. Currently, the measurement of FT3, FT4 and TSH is the preferred index for evaluating thyroid function. The measurement of TSH level can be used as an indicator to observe the efficacy of thyroxine replacement therapy in hypothyroid patients.