预期应用
ELISA法定量测定大鼠血清、血浆、或其它相关液体中甲状腺素（T4）含量。
概述
T4是甲状腺分泌的二种主要激素之一，分子量777D，全部由甲状腺产生。其主要作用是促进合成和能量代谢，使基础代谢率和耗氧量增加，促进生长和发育。在血液循环中主要以与甲状腺结合蛋白质结合的形式存在。T4的合成和分泌主要受下丘脑和垂体的控制。是甲状腺功能主要诊断指标。
实验原理
本试剂盒应用竞争抑制酶标免疫分析法测定标本中T4水平。用纯化的抗体包被微孔板，制成固相抗体，固相抗体与一定量的生物素标记的T4和非标记抗原(标本或标准品)进行竞争抑制反应，待测定的标本量越多，抗体与生物素标记的T4结合就越少，反之结合就多。最后再加入HRP标记的亲和素，经过彻底洗涤后用底物TMB显色。TMB在过氧化物酶的催化下转化成蓝色，并在酸的作用下转化成最终的黄色。颜色的深浅和样品中的T4呈负相关。用酶标仪在450nm波长下测定吸光度（OD值），计算样品浓度。 本产品采用超敏感的显色系统显著提高检测的灵敏程度。
Intended use
This immunoassay kit allows for the specific Ultrasensitivity measurement of Rat T4 concentrations in plasma and serum.
Introduction
Thyroxine (T4), the principal thyroid hormone largely bound to transport proteins, especially TBG. Given normal levels of thyroid hormone-binding proteins, hyperthyroidism is characterized by increased levels of circulating T4, hypothyroidism by decreased levels. Exceptions to this parallelism between thyroid status and total T4 concentration are found. Levels of TBG are known to be altered under various physiological, pharmacological and genetic conditions. Thus, elevated T4 levels may be obtained when TBG levels are high, as in pregnancy, acute intermittent porphyria, hyperproteinemia, hereditary TBG elevation and in patients undergoing estrogen therapy or taking oral contraceptives. Total T4 levels may be depressed when TBG levels are low, as in nephrotic, hepatic, gastrointestinal and neoplastic disorders; in acromegaly, hypoproteinemia and hereditary TBG deficiency; and in patients undergoing androgen, testosterone or anabolic steroid therapy. Diphenylhydantoin and large doses of salicylates and liothyronine may also cause low T4 values (not reflective of thyroid status) due to their competition fo binding sites on TBG.
Test principle
This assay employs the competitive inhibition enzyme immunoassay technique. A monoclonal
antibody specific for T4 has been pre-coated onto a microplate. A competitive inhibition reaction is launched between biotin labeled T4 and biotin unlabeled antigens (Standards or samples) with the pre-coated antibody specific for T4. The more the amount of T4 in samples, the less the biotin labeled T4 bound by pre-coated antibody. Then HRP labeld avidin and substrate solution are added to the wells, respectively. And the color develops in opposite to the amount of T4 bound in the initial step. The color development is stopped and the intensity of the color is measured. This assay uses the novel enzyme reagent system to increase the sensitivity of measurement for T4. | 
