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TEST ITEMS

THE GENERATION DIAGNOSTIC SYSTEM

T4

Thyroxine (T4) is one of two major hormones produced by the thyroid gland (the other is called triiodothyronine, or T3). T4 and T3 are regulated by a sensitive feedback system involving the hypothalamus and the pituitary gland. The hypothalamus releases the thyrotropin releasing hormone (TRH), which stimulates the pituitary to release the thyroid stimulating hormone (TSH). This causes the thyroid to release T3 and T4 and these in turn regulate the release of TRH and TSH via a feedback control mechanism. Normally, elevated blood levels of T4 and T3 act to decrease the amount of TSH secreted, thereby reducing the production and release of T4 and T3. Over 99% of T4 is reversibly bound to three plasma proteins in blood: thyroxine binding globulin (TBG) binds close to 70%, thyroxine binding pre-albumin (TBPA) binds 20%, and albumin binds 10%. Approximately 0.03% of T4 is in the free, unbound state in blood at any one time. T4 is a useful marker for the diagnosis of hypothyroidism and hyperthyroidism. The level of T4 decreases in hypothyroidism, myxedema and chronic thyroiditis (Hashimoto’s disease). Increased levels of T4 have been found in hyperthyroidism due to Grave’s disease and Plummer’s disease.

References

  • 1. Thakur C., Saikia T.C. Yadav R.N., Total serum levels of triiodothyronin(T3) thyroxine(T4) and thyrotropine(TSH) in school going children of Dibrugarh district: an endemic goiter region of Assam. Indian J Physiol Pharmacol, 1997, 41(2) : 167-170
  • 2. Larsen P.R., Dockalova J., Sipula D., Wu F. M. Immunoassay of Thyroxine in unextracted Human Serum. J. Clin. Endocrinol. Metabl., 1973, 37(2):177-182
  • 3. Wagner M. S., Wajner S. M., Maia A. L. The Role of Thyroid Hormone in testicular Development and Function. J. Endocrinol., 2008, 199(3) : 351-365
  • 4. Wahlin A., Wahlin T. B., Small B. J., Backman L. Influences of thyroid stimulating hormone on cognitive functioning in very old age. J. Gerontol B. Psychol Sci. Soc. Sci., 1998, 5 : 234-239
  • 5. Willian R. Kirk, et al. Characterization of the sources of protein-Ligand Affinity:1-sulfonato-8-(1’) anilinonaphthalene Binding to intestinal Fatty Acid binding protein. Biophysical Jounal(1996) pp.69-83
  • 6. Jeramia K. Ory and Leonard J. Banaszak. Studies of the Binding Reaction of Adipocyte Lipid Binding Protein using the Fluorescent Probe 1,8-Anilinonaphthalene-8-Sulfonate. Biophysical Journal(1999) pp.1107-1116
  • 7. Toshiro Sakurada, et al. Radioimmunoassay for serum Thyroxine. Tohoju J.(1976) pp.125-133

ichroma™

Compatible Device ichroma™ I/II
Detection Range 10.23~300.0nmol/L
Sample Type Serum, Plasma
CV <10%
Comparability 0.965
Reaction Time 16Min

AFIAS

Compatible Device AFIAS-1/6
Detection Range 10.23~300.0nmol/L
Sample Type Serum, Plasma
CV <10%
Comparability 0.965
Reaction Time 16Min

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