• Assay Type Competitive ELISA
  • Sample Types Serum, Plasma, Urine, Fecal Extracts, Tissue Culture Media
  • Sensitivity 0.23 ng/mL
  • Species Thyroxine is identical across species
  • Assay Duration 1.5 Hours
  • Samples/Plate 40 in Duplicate
  • Readout Colorimetric, 450 nm
  • Standard Curve Thyroxine (T4) ELISA Kit
  • Description

    Assay Principle: 

    The Thyroxine (T4) ELISA Kit quantitatively measures T4 in serum, plasma, urine, fecal extracts, and tissue culture media. The Thyroxine (T4) ELISA Kit is a competitive ELISA with a run time of 1.5 hours. Please read the complete kit insert for more information before performing this assay.

    Use our provided T4 standard to generate a standard curve for the assay. Pipette the standards or diluted samples into a transparent microtiter plate coated with our goat anti-mouse IgG antibody. Add the T4 peroxidase conjugate and the T4 monoclonal mouse antibody. Then incubate the mixture covered at room temperature, shaking for 1 hour. The immunological reaction occurs between the anti-T4 antibody, the T4 antigen in the sample or standard, and the T4-peroxidase conjugate. As the T4 concentration in the sample increases, the bound T4-peroxidase conjugate decreases, causing a decrease in signal and vice versa. 

    After the 1-hour incubation, wash away the excess T4-peroxidase conjugate and add the TMB substrate. The TMB substrate reacts with the bound T4-peroxidase conjugate generating a signal detected by a plate reader at 450nm. Use the intensity and the standard curve to calculate the T4 concentration in the samples.


    The thyroid hormones triiodothyronine (T3) and thyroxine (T4) are tyrosine-based hormones the thyroid gland produces that regulate metabolism. Iodine is necessary for the production of T3 and T4. A deficiency of iodine leads to decreased production of T3 and T4, enlarges the thyroid tissue, and causes the disease known as goiter. The primary form of thyroid hormone in the blood is T4, which has a longer half-life than T3. The ratio of T4 to T3 released into the blood is roughly 20 to 1. T4 is converted to the active T3 (three to four times more potent than T4) within cells by deiodinases. All three deiodinase isoforms are selenium-containing enzymes; thus, dietary selenium is essential for T3 production.

    Hypothyroidism is the condition that results from the under-production of thyroxine by the thyroid gland, either because the gland is naturally underactive or because radioiodine therapy or surgery for an overactive gland has resulted in under activity. Patients commonly take thyroxine to replace the deficiency in such situations, restoring regular metabolic activity. The concentration of T3 and T4 in the blood regulates the pituitary release of thyrotropin in a negative feedback loop such that when T3 and T4 concentrations are high, TSH production is reduced.