T3, T4, and TSH – Thyroid Function Test Details & Interpretation

What Are T3, T4, and TSH?

These are key hormones involved in regulating metabolism, energy levels, and overall body function:

1. TSH (Thyroid Stimulating Hormone) – Produced by the pituitary gland; controls thyroid hormone production.
2. T3 (Triiodothyronine) – The active thyroid hormone; regulates metabolism and energy.
3. T4 (Thyroxine) – The storage form of thyroid hormone; gets converted into T3 when needed.

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Why is the T3, T4, TSH Test Done?

✅ Diagnose thyroid disorders (Hypothyroidism, Hyperthyroidism)
✅ Monitor thyroid medication (Levothyroxine, Anti-thyroid drugs)
✅ Evaluate symptoms like fatigue, weight changes, or heart rate issues
✅ Screen for thyroid problems in pregnancy

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Normal Reference Ranges (May vary by lab)

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Interpreting T3, T4, TSH Test Results

1. Hypothyroidism (Underactive Thyroid)

🔴 High TSH, Low Free T4 (sometimes low T3)
✔ Symptoms: Fatigue, weight gain, cold intolerance, dry skin, depression
✔ Possible Causes:

• Hashimoto’s Thyroiditis (Autoimmune)
• Iodine Deficiency
• Post-thyroidectomy (after thyroid removal)
  ✔ Treatment: Levothyroxine (T4 replacement therapy)

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2. Hyperthyroidism (Overactive Thyroid)

🔴 Low TSH, High Free T4 and/or T3
✔ Symptoms: Weight loss, anxiety, rapid heartbeat, sweating, tremors
✔ Possible Causes:

• Graves’ Disease (Autoimmune)
• Toxic Nodular Goiter
• Thyroiditis (inflammation of the thyroid)
  ✔ Treatment: Anti-thyroid drugs (Methimazole, PTU), Beta-blockers, or Surgery

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3. Subclinical Hypothyroidism

🔴 Mildly High TSH, Normal Free T4 & T3
✔ No major symptoms, but may progress to full hypothyroidism
✔ Treatment depends on TSH level & symptoms

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4. Subclinical Hyperthyroidism

🔴 Low TSH, Normal Free T4 & T3
✔ Often no symptoms, but may increase risk of osteoporosis & heart disease
✔ Treatment may not be needed unless symptoms appear

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Additional Thyroid Tests (If Needed)

🔹 Anti-TPO (Thyroid Peroxidase Antibodies) – For diagnosing Hashimoto’s or Graves’ Disease
🔹 Thyroid Ultrasound – If nodules or enlargement are suspected
🔹 Thyroid Uptake Scan – For evaluating overactive thyroid conditions