In the process of thyroid metabolism, the T4 5 in the outer ring of the formation of iodine T3, while in the inner ring of the iodine on the
In the process of thyroid metabolism, the T4 5 in the outer ring of the formation of iodine T3, while in the inner ring of the iodine on the 5 position that is the formation of the 3, '' '-T3', known as anti T3 (reverse T3, rT3,). Under normal circumstances, about 55% of the daily T4 to rT3. Most of rT3 (95%-98%) was formed by T4, and only 2%-5% was secreted by the thyroid gland. The product of T4 iodine removal depends on the state of the body, when the physiological activities need more active thyroid hormones (such as when the body is in a cold state), T4 and iodine into T3 more than rT3; when the stress, hunger, pregnancy, metabolic disorders, liver disease, renal failure and other conditions, T4 removal of iodine into rT3 the increase in the proportion of. During the period of 40 years old, rT3 decreased with the increase of age, and the age of more than 40 years showed an increasing trend with age. RT3 has no obvious biological activity, and decays rapidly in the body fluid or cell, so it can not be biological, so T4 can be regarded as rT3 inactivation process. 98% of the rT3 in the blood circulation is bound to rT3 binding protein (TBG), so the change of TBG can directly affect the value of the assay. Clinical significance of rT3:
A, rT3 elevated common disease
1 the concentration of rT3 in the blood circulation of hyperthyroidism was higher than that of T3 and T4, and the diagnostic coincidence rate was up to 100%.
2 non thyroid diseases such as acute myocardial infarction, cirrhosis, diabetes, uremia, cerebrovascular accident, gastric cancer, heart failure, acid poisoning, endocarditis fever and other infectious disease were increased rT3.
3 other drugs (such as amiodarone, propranolol, dexamethasone, propylthiouracil, etc.) TBG disease and the elderly increased rT3.
Two, rT3 reduce common diseases
1 hypothyroidism in light of hypothyroidism and subclinical hypothyroidism diagnosis, some people think that rT3 is superior to T3 and T4. It has been reported for rT3 hypothyroidism (0.1 + 0.03) nmol/L.
2 chronic lymphocytic thyroiditis rT3 to the disease into a potential value in the early hypothyroidism or observation.
3 guidance in the treatment of hyperthyroidism rT3 decreased faster, rT3 decreased slowly, if rT3 and T4 were lower than normal, suggesting excessive dosage. In patients with hypothyroidism with thyroid hormone replacement therapy, if rT3 and T3 were increased, while T4 may still normal, that the dosage is too large. Some scholars believe that high RT3 shows that not only the inhibitor rT3 into the cell, and can increase the T4 in order to facilitate the formation of rT3. RT3 is an excellent marker reflecting the reduced T4 and T3 levels of cells, even though the reduced T4 and T3 levels in cells were not detected by TSH or T4 and T3. High or high normal rT3 tissue is not only an index of hypothyroidism, but in this case only replaced by T4 (rT3) is not considered to be the best, is expected to appear inappropriate or suboptimal results.