Thyroxine, the main thyroid hormone, circulates in the blood almost completely bound to transporter proteins. The main carrier is thyroxine-binding globulin (TBG). However, only free thyroxine is responsible for the biological action. The increase in total thyroxine associated with pregnancy, oral contraceptives, and estrogen therapy occasionally results in total T4 levels above normal limits, while the free thyroxine concentration remains in the normal reference range.
Masking of abnormal thyroid function can also occur in both hyper and hypothyroid conditions due to alterations in TBG concentration. Total T4 can be raised or lowered by changes in TBG so that normal reference levels result. The concentration of free thyroxine can help to discover the actual clinical status of the patient.
Free ELISA T4 Test Principle:
The free T4 ELISA is based on the principle of a solid phase enzyme-linked competitive enzyme immunoassay. The essential reagents required for a solid-phase enzyme immunoassay include an immobilized antibody, enzyme-antigen conjugate, and native antigen.
By mixing immobilized antibody, enzyme-antigen conjugate, and a serum containing the native free antigen, a competition reaction occurs between the native free antigen and the enzyme-antigen conjugate for a limited number of insolubilized binding sites. For more details, see the instructions for use.
Diagnostic Automation Inc. also provides other Thyroid ELISA kits. For more information on ELISA kits, rapid tests, IFA kits, CLIA test kits, or serological tests, please see the home page of our website or contact our customer service representatives at 818-591- 3030.
This free T4 ELISA test kit assay, the use of several serum references of known free thyroxine concentration allows the construction of an activity and concentration graph. From comparison with the dose-response curve, the activity of an unknown sample can be correlated with the free thyroxine concentration.