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MEDICA 2019 - World Forum for Medicine
Düsseldorf, GermanyBooth No.: 3/D35-2
AACC Annual Scientific Meeting and Clinical Lab Expo
Anaheim Convention Center ~ Anaheim, CABooth No.: 2627
Thanks to Block Scientific, I was able to procure the re-certified Bayer DCA 2000+ without hassles and get the lab back in operation. The
device works perfectly and I look forward to doing more business with Block Scientific.
--- Mathew Anderson, New Jersey
For the quantitative determination of Free Thyroxine (fT4) concentration in Human serum.
L-Thyroxine (T4) or 3,5,3’,5’-tetraiodothyronine is the most commonly measured thyroid hormone for the diagnosis of thyroid function. T4 has its primary infuence on protein synthesis and oxygen consumption in virtually all tissues but it is also important for growth, development, and sexual maturation.
T4 is synthesized by the thyroid gland and is secreted into the bloodstream. Here the T4 becomes bound to serum proteins for transport to the cells. The major transport protein is Thyroxine Binding Globulin (TBG) which normally accounts for 80% of the bound T4. Other thyroid hormone binding proteins are Thyroxine Binding Prealbumin and Albumin. Most of the serum T4 is bound to these transport proteins leaving only about 0.03% free to exert its effect on cells. It is the free T4 (fT4) that represents the metabolically active fraction; for this reason the measurement of
fT4 concentration is considered to be an indicator of patient thyroid status.
Primary hypothyroidism results in underproduction of T4 by the thyroid gland and consequently an abnormally low circulating fT4 concentration in the blood. Primary hyperthyroidism leads to excessive thyroid production on T4 and resulting elevated fT4 concentration. Total serum T4 concentrations are dependent on the level of circulating TBG as well as the patient’s thyroid status. The concentration of TBG can be affected by certain drugs, steriod hormones, pregnancy, and by various nonthyroid illnesses.
In an earlier generation of thyroid function tests, the effect of variable TBG concentration was dealt with by calculating a Free Thyroxine Index (FTI). This FTI is the product of Total T4 concentration and Thyroid Uptake (TU), which assesses the number of available binding sites on the TBG. This approach requires carrying out two separate assay determinations (total T4 and TU), but does provide a better indicator of thyroid status than total T4 alone. fT4 tests are designed to directly reflect the equilibrium existing in serum between T4 and TGB-bound T4. These methods, including this fT4 test, can generally reflect thyroid status in a single assay.