KTE0005 | EliKine™ Free Thyroxine (fT4) ELISA Kit — The Gold Standard for Thyroid Function Assessment

fT4: The Thyroid‘s Primary Secretory Product, Measured at Its Bioactive Core

Thyroxine (T4) is the principal hormone secreted by the thyroid gland—accounting for approximately 90% of thyroid hormone output. But here is the catch: over 99% of circulating T4 is bound to carrier proteins, primarily thyroxine-binding globulin (TBG)[reference:25]. Only the free, unbound portion (free T4, or fT4) is biologically active[reference:26]. In normal thyroid function, as carrier protein concentrations fluctuate, total T4 levels change to maintain constant free T4[reference:27]. This makes fT4 the most reliable indicator of actual thyroid status—particularly when TBG levels are altered by pregnancy, estrogen therapy, liver disease, or genetic conditions[reference:28]. The EliKine™ Free Thyroxine (fT4) ELISA Kit (KTE0005) delivers precise, reproducible fT4 quantification.

Competitive ELISA: Engineered for Free Hormone Accuracy

KTE0005 employs the competitive inhibition enzyme immunoassay technique[reference:29]. The microtiter plate is pre-coated with an antibody specific to fT4. Standards or samples compete with biotin-conjugated fT4 for binding to the immobilized antibody[reference:30]. The more fT4 in your sample, the less biotin-conjugated fT4 binds[reference:31]. After washing, avidin-HRP is added, substrate is introduced, and color develops inversely proportional to fT4 concentration[reference:32]. This competitive format is specifically optimized to measure free hormone in the presence of abundant binding proteins.

Calibration Range and Sensitivity That Matter

• Calibration Range: 4 pmol/L – 64 pmol/L[reference:33]
• Limit of Detection: 4.0 pmol/L[reference:34]
• Assay Type: Competitive ELISA (quantitative)[reference:35]
• Sample Types: Serum, Plasma, Other biological fluids[reference:36]
• Assay Duration: 3–4 hours[reference:37]

Broad Species Reactivity

Validated across Bovine, Chicken, Dog, Goat, Human, Monkey, Mouse, Rabbit, Rat, Sheep, and Swine[reference:38]—supporting translational research across multiple model systems.

Complete Kit Components

The kit includes: fT4 microplate, fT4 standard, Biotin-conjugated fT4, Avidin-HRP, HRP substrate A & B, Stop solution, Wash buffer, and Plate covers[reference:39].

No Significant Cross-Reactivity

Rigorous validation confirms no significant cross-reactivity or interference between fT4 and analogues[reference:40]. When you measure fT4, you measure fT4—not cross-reacting metabolites.

Who Needs This Kit?

• Endocrinologists diagnosing and monitoring thyroid disorders
• Toxicologists assessing thyroid-disrupting chemicals
• Pharmacologists evaluating drug effects on thyroid function
• Reproductive biologists studying thyroid hormone in pregnancy
• Clinical researchers developing thyroid function biomarkers

🔗 Reference Link: https://www.abbkine.com/product/elikine-free-thyroxine-ft4-elisa-kit-kte0005/