Total triiodothyronine (TT3) represents the entire circulating pool of T3, encompassing both the protein-bound (~99.7%) and the biologically active free fraction (~0.3%). Approximately 20% of T3 is secreted directly by the thyroid gland, whereas 80% arises from peripheral conversion of T4 in liver, muscle, kidney, and brain. Clinically, elevated TT3 may indicate hyperthyroidism, T3 toxicosis (elevated T3 with normal T4), or excessive thyroid hormone replacement. Conversely, reduced TT3 is observed in advanced hypothyroidism, severe systemic illness, starvation, chronic stress, and non-thyroidal illness syndrome (euthyroid sick syndrome).

The RayBio^® Total T3 Enzyme Immunoassay (EIA) Kit is a competitive immunoassay designed to quantify T3 in human, mouse, rat, porcine, feline, canine, equine, and sheep serum or plasma, as well as urine samples, within 3 hours. Absorbance is measured at 450 nm, and concentrations are interpolated from a ready-to-use T3 standard curve. The assay demonstrates a sensitivity of 0.167 ng/dL and has been validated for linearity, stability, precision, and spike-recovery performance. Each kit provides sufficient reagents to perform up to 96 assays, including standard curve and unknown samples.

• Various species
• High sensitivity
• Rapid detection within 2.5 hours
• Good characteristics in terms of linearity, stability, precision, and spiking & recovery

• Pre-Coated 96-well Strip Microplate
• Assay Diluent
• Treatment Buffer
• Lyophilized Standard
• Positive Control
• Capture Antibody
• HRP-conjugated Secondary Antibody
• Wash Buffer
• TMB One-Step Substrate Reagent
• Stop Solution

• Microplate reader capable of measuring absorbance at 450 nm
• Precision pipettes to deliver 2 μL to 1 mL volumes
• Adjustable 1-25 mL pipettes for reagent preparation
• 100 mL and 1-liter graduated cylinders
• Distilled or deionized water
• Tubes to prepare standard or sample dilutions
• Orbital shaker
• Software which can perform four-parameter logistic regression models

1. Prepare all reagents, samples and standards as instructed.
2. Add 50 µL standards or samples to appropriate well. Incubate for 10 minutes at room temperature.
3. Add 50 µL Capture Antibody to appropriate well. Incubate 1 hour at room temperature. And wash 5 times.
4. Add 100 µL prepared HRP-Secondary Antibody solution. Incubate 1 hour at room temperature. And wash 5 times.
5. Add 100 µL TMB One-Step Substrate Reagent to each well. Incubate 5-20 minutes at room temperature.
6. Add 50 µL Stop Solution to each well. Read at 450 nm immediately.