Total T3 test kit EIAgen

for thyroid diseasesprealbuminserum

EIAgen Total T3 Kit is a direct solid phase enzyme immunoassay for the quantitative measurement of total 3,5,3’-triiodothyronine (T3) in human serum or plasma. Introduction Thyroxine (T4) and 3,5,3’-triiodothyronine (T3) are the two principal thyroid hormones. In contrast to T4, which is exclusively a product of the thyroid gland, T3 is mainly produced in the peripheral tissues by 5’-monodeiodination of circulating T4. In normal adults about 80% of T3 is produced by peripheral conversion and about 20% is secreted directly by the thyroid. A small amount of T4 is 5-monodeiodinated to form 3,3’,5’-triiodothyronine (reverse T3); this is probably biologically inactive. The proportion of T4 converted to reverse T3 may be increased under certain circumstances, such as severe illness or medication with Amodiarone or radiographic contrast agents. This reduces the production and hence the circulating level of T3. Considerable evidence exists to show that T3 is the more active thyroid hormone and some authors have suggested that T4 has no intrinsic activity. Both T3 and T4 circulate in association with serum proteins, the most important of which is thyroxine binding globulin (TBG). This has a higher affinity for T4 than for T3. Approximately 80% of circulating T3 is bound to TBG. Most of the rest is bound to prealbumin and albumin; only about 0.5% of T3 is “free” in serum (i.e. not bound to serum proteins). The concentration of T3 in serum can be alterated by a change in the activity of the thyroid gland or by alteration in the peripheral metabolism of T4.