Total T3

GWB-74C5DC

The triiodothyronine (T3) is a tyrosine-based hormones produced by the thyroid gland. An important component in the synthesis is iodine. Thyroxine-binding globulin (TGB) is the major carrier protein for circulating thyroid hormone. Only the free fraction of T3 is biologically active a very small fraction of the circulating hormone is unbound - T3 0. 3%. The thyronines act on the body to increase the basal metabolic rate affect protein synthesis and increase the body\' s sensitivity to catecholamines (such as adrenaline) by permissiveness. The thyroid hormones are essential to proper development and differentiation of all cells of the human body. These hormones also regulate protein fat and carbohydrate metabolism affecting how human cells use energetic compounds. Numerous physiological and pathological stimuli influence thyroid hormone synthesis. Both excess and deficiency of thyroxine can cause disorders. Thyrotoxicosis or hyperthyroidism is the clinical syndrome caused by an excess of circulating free thyroxine free triiodothyronine or both. It is a common disorder that affects approximately 2% of women and 0. 2% of men. Hyperthyroidism is the case where there is a deficiency of thyroxine. Release of T3 from the thyroid gland into the blood is ~5-8 micrograms/day. In addition approximately 22 mg/day of T3 is produced by nonthyroidal 5-monodeionination of T4. T3 has a much faster turnover than T4 (T ~1 day compared to ~6 days for T4) and has greater biological potency than T4. Several drugs are known to affect the binding of Triiodothyronine to the thyroid hormone carrier proteins or its metabolism to T3 and complicate the interpretation of T3 results. Circulating autoantibodies to T3 and hormone-binding inhibitors may interfere. Measurement of total serum T3 concentrations is a standard and well-validated test of thyroid gland function. Principles of the assay: Microtiter strip wells are precoated with anti-T3 antibodies (solid-phase). T3 in the sample competes with added horseradish peroxidase labelled T3 (enzyme-labelled antigen) for antibody binding. After incubation a bound/free separation is performed by solid-phase washing. The immune complex formed by enzyme-labelled antigen is visualized by adding Tetramethylbenzidine (TMB) substrate which gives a blue reaction product. The intensity of this product is inversely proportional to the amount of T3 in the sample. Sulphuric acid is added to stop the reaction. This produces a yellow endpoint colour. Absorption at 450 nm is read using an ELISA microwell plate reader. Storage and Stability: The reagents are stable up to the expiry date stated on the label when stored at +2. . . +8 & deg; C in the dark. Opened reagents are stable for another 60 days if stored at 2?8& deg; C. Limitations of the Test: Bacterial contamination or repeated freeze-thaw cycles of the specimen may affect the absorbance values. References Gharib H. Ryan R. J. Mayberry W. E. and Hockett T. ; J. Clinical Endocrinol. (1971) 33 509Chopra I. J. Ho R. S. and Lam R. ; J. Lab. Clinical Med. (1971) 80 729Young D. S. Pestaner L. C. and Gilberman U. ; Clinical Chemistry (1975) 21 3660Sterling L. ; Diagnosis and Treatment of Thyroid Disease Cleveland CRC Press (1975) p. 9-51