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The Free T3, Free T4 & TSH test — commonly called Free TFT (Free Thyroid Function Test) — measures the biologically active, unb...
Also known as: Free TFT · Free Thyroid Function Test · FT3 FT4 TSH Test · Free Triiodothyronine Free Thyroxine TSH
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*Inclusive of home collection charges
The Free T3, Free T4 & TSH test — commonly called Free TFT (Free Thyroid Function Test) — measures the biologically active, unbound fractions of the two thyroid hormones alongside TSH. Unlike total T3 and T4 (which include both active and inactive protein-bound fractions), Free T3 and Free T4 reflect only the hormones actually available to cells — giving a more accurate measure of true thyroid hormone activity, particularly when blood proteins are abnormal (as in pregnancy, liver disease, nephrotic syndrome, or oestrogen therapy). No fasting required.
Key benefits of this package include:
What Does the Free T3, Free T4 & TSH Test (Free TFT) Measure?
| Level / Result | Possible Interpretation |
|---|---|
| TSH normal + FT4 normal + FT3 normal | Normal thyroid function — euthyroid state |
| TSH elevated + FT4 low (Overt hypothyroidism) | Underactive thyroid — levothyroxine therapy required |
| TSH elevated + FT4 normal (Subclinical hypothyroidism) | Early thyroid underactivity — monitor or treat based on TSH level and symptoms |
| TSH low + FT4 elevated + FT3 elevated (Overt hyperthyroidism) | Overactive thyroid — Graves' disease, toxic nodule; antithyroid treatment required |
| TSH low + FT3 elevated + FT4 normal (T3 toxicosis) | Free T3-driven hyperthyroidism — early Graves', toxic nodule, or excess T3 intake |
| TSH low + FT4 elevated + FT3 normal | Exogenous T4 (levothyroxine) intake or early hyperthyroidism — review dose or investigate |
| Low TSH + Normal FT4 + Normal FT3 in pregnancy (1st trimester) | Physiological — hCG stimulates thyroid in first trimester, transiently lowering TSH; usually self-limiting |
Important Note: Free TFT interpretation requires understanding the clinical context — particularly pregnancy status, protein-altering conditions, and current thyroid medications. TSH remains the most sensitive indicator of thyroid status; Free T3 and Free T4 provide the full picture when TSH is abnormal. Pregnancy-specific TSH reference ranges must be applied in pregnant patients. All results must be reviewed by a physician or endocrinologist.
Thyroid in Pregnancy — Why Free TFT Is Essential: Thyroid function is uniquely complex during pregnancy. hCG (human chorionic gonadotropin) — the pregnancy hormone — stimulates TSH receptors, causing TSH to fall transiently in the first trimester (sometimes below the normal non-pregnant range — this is physiological, not hyperthyroidism). Simultaneously, oestrogen rises substantially, increasing TBG production and raising total T4 — but Free T4 remains stable. Using non-pregnant reference ranges or total T3/T4 values in pregnancy leads to misinterpretation. Trimester-specific TSH ranges and Free T4 are the correct parameters for pregnant patients.
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