Why is Free T4 Index (T7) important?

FTI provides a more accurate assessment of thyroid function when binding protein levels are abnormal (pregnancy, oral contraceptives, liver disease). It estimates the amount of thyroid hormone available to tissues regardless of binding protein changes.

What are the symptoms of abnormal Free T4 Index (T7) levels?

High FTI (hyperthyroidism): Weight loss, rapid heartbeat, anxiety, tremor, heat intolerance, diarrhea. Low FTI (hypothyroidism): Fatigue, weight gain, cold intolerance, constipation, dry skin, depression.

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Free T4 Index (T7)

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The Free Thyroxine Index (FTI or T7) estimates free T4 by multiplying total T4 by T3 uptake, correcting for binding protein variations.

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FTI provides a more accurate assessment of thyroid function when binding protein levels are abnormal (pregnancy, oral contraceptives, liver disease)
It estimates the amount of thyroid hormone available to tissues regardless of binding protein changes

Total T4 × T3 Uptake

The Free Thyroxine Index (FTI or T7) estimates free T4 by multiplying total T4 by T3 uptake, correcting for binding protein variations

High FTI (hyperthyroidism): Weight loss, rapid heartbeat, anxiety, tremor, heat intolerance, diarrhea.
Low FTI (hypothyroidism): Fatigue, weight gain, cold intolerance, constipation, dry skin, depression.

High FTI: Hyperthyroidism (Graves' disease, toxic nodule), thyroiditis, excess thyroid medication.
Low FTI: Primary hypothyroidism, pituitary dysfunction, severe illness.

This is a calculated biomarker derived from other test results in your panel. It provides additional clinical insights by combining multiple measurements into a single meaningful ratio or index.

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Free T4 Index (T7)

About Free T4 Index (T7)

How It's Calculated

Why Free T4 Index (T7) Matters

Symptoms of Free T4 Index (T7)

What Affects Free T4 Index (T7) Levels

How it works: 4 easy steps

Choose your tests

Quick & convenient testing

Clear, personalized results

Optimize your health

Our Comprehensive Panels

Explore Other Tests

Basophils

Apolipoprotein B

Nitrite

Monocyte-to-Lymphocyte Ratio (MLR)

Our Customers Says

Have questions?