THYROID HEALTH CHECKUP Lab Tests

🧪 Thyroxine-Binding Globulin (TBG) Test The Thyroxine-Binding Globulin (TBG) test measures the amount of TBG protein in your blood. TBG is a transport protein that binds to thyroid hormones (T3 and T4) and carries them through the bloodstream. It’s not a routine thyroid function test, but it’s useful in special cases when thyroid hormone levels seem abnormal but TSH, Free T3, and Free T4 don’t fully explain symptoms. 🧬 What Is TBG? Feature Description Full Name Thyroxine-Binding Globulin Main Role Binds to and transports T3 and T4 Bound Hormones Are inactive (only free hormones are active) Produced by Liver 📊 Normal Reference Range (May vary by lab) Test Normal Range TBG 15 – 30 µg/mL (or) 1.3 – 2.0 mg/L 📈 High or 📉 Low TBG – What It Means 📈 Increased TBG More hormone is bound, less Free T4/T3 available (but Total T4/T3 may be high) Causes: Pregnancy (due to estrogen) Estrogen therapy (e.g., oral contraceptives) Hepatitis Genetic increase in TBG 📉 Decreased TBG Less hormone is bound, more Free T4/T3 relative to Total Causes: Liver disease Nephrotic syndrome Corticosteroid use Androgens or anabolic steroids Genetic TBG deficiency 🧪 Why Is the TBG Test Done? Use Case Purpose Unexplained high or low Total T4/T3 To assess if altered due to binding issues Pregnancy or hormone therapy Understand changes in thyroid tests Suspected inherited TBG disorder Evaluate genetic binding protein conditions 🧾 Example Lab Report Test Result Reference Range Thyroxine-Binding Globulin 28 µg/mL 15 – 30 µg/mL ✅ Interpretation: TBG within normal limits — does not affect total/free T3/T4 interpretation. 🧠 Important Notes TBG does not measure thyroid hormone levels directly. Use Free T3 and Free T4 to assess actual thyroid hormone activity. If Total T4 is high and Free T4 is normal, elevated TBG might be the reason. ✅ Summary Feature Details Test Thyroxine-Binding Globulin (TBG) Function Binds and transports thyroid hormones High TBG Seen in pregnancy, estrogen therapy Low TBG Seen in liver disease, steroid use Best Used With Total and Free T4/T3 levels

🧪 Thyroglobulin (Tg) Test The Thyroglobulin test measures the level of thyroglobulin, a protein produced only by thyroid tissue — both normal and cancerous. It is most often used as a tumor marker in patients who have had thyroid cancer, particularly papillary or follicular thyroid cancer. 🧬 What Is Thyroglobulin? A glycoprotein made by the thyroid gland. Acts as a precursor in the synthesis of T3 and T4 hormones. Not usually measured to assess thyroid function in healthy people. 🧪 Why Is the Test Done? Purpose Use Case Tumor marker To monitor for recurrence of thyroid cancer after thyroidectomy Effectiveness of treatment To check if radioactive iodine or surgery was successful Diagnostic tool (rarely) May help evaluate thyroiditis or thyroid nodules in some cases ⚠️ Thyroglobulin is only useful in patients who still have thyroid tissue. If the thyroid is removed or ablated, levels should be very low or undetectable. 📊 Normal Reference Range (may vary) Test Normal Range Thyroglobulin < 55 ng/mL (typical) Reference values depend on the lab and whether anti-thyroglobulin antibodies (TgAb) are present. 🔍 Anti-Thyroglobulin Antibodies (TgAb) These can interfere with thyroglobulin measurements. Always check TgAb levels when measuring thyroglobulin. If TgAb is positive, the Tg result may be falsely low or high. 📈 Elevated Thyroglobulin – What It Means Condition Likely Reason Thyroid cancer recurrence Possible regrowth or metastasis Thyroid inflammation Thyroiditis (e.g., Hashimoto’s, subacute) Goiter or nodules Benign or malignant enlargement Thyroid hormone therapy May decrease Tg, used to monitor response 🧾 Example Lab Report Test Result Reference Range Thyroglobulin 1.2 ng/mL < 55 ng/mL Anti-Tg Ab Negative Negative ✅ Interpretation: Low Tg with negative antibodies — no evidence of thyroid tissue activity or cancer recurrence. 🚩 What If Thyroglobulin Is High After Thyroidectomy? May suggest: Residual thyroid tissue Recurrent or metastatic cancer A rising trend is more important than a single result. Doctors often use thyroglobulin levels + neck ultrasound to monitor recurrence. ✅ Summary Feature Details Test Thyroglobulin (Tg) Use Tumor marker for thyroid cancer follow-up High Value Possible recurrence, inflammation, or residual tissue Key Companion Test Anti-Tg Antibody (TgAb) Not for Routine thyroid function testing

🧪 Anti-TPO Antibodies (Anti-Thyroid Peroxidase Antibodies) The Anti-TPO antibody test measures antibodies against thyroid peroxidase (TPO) — an enzyme crucial for producing thyroid hormones (T3 and T4). These antibodies indicate an autoimmune attack on the thyroid and are key markers for thyroid autoimmune diseases. 🧬 What Are Anti-TPO Antibodies? Thyroid peroxidase (TPO) is an enzyme in the thyroid gland that helps make thyroid hormones. Anti-TPO antibodies form when the immune system mistakenly targets TPO, disrupting hormone production. 📊 Normal Reference Range (May vary slightly between labs) Test Normal Range Anti-TPO Ab < 35 IU/mL (or) Negative ⚠️ High Anti-TPO Antibody Levels – What It Means Condition Notes Hashimoto’s thyroiditis Most common cause of hypothyroidism Graves’ disease Can also be elevated (hyperthyroidism) Postpartum thyroiditis Can predict risk in at-risk women Autoimmune thyroiditis (general) Marker of immune activity against thyroid ✅ Up to 90–95% of Hashimoto’s and 70–80% of Graves' patients have elevated Anti-TPO antibodies. 🧾 Example Lab Report Test Result Reference Range Anti-TPO Antibodies 120 IU/mL < 35 IU/mL ✅ Interpretation: Elevated — consistent with autoimmune thyroiditis. Interpretation should be made alongside TSH, Free T4, and Free T3. 📈 Clinical Use of Anti-TPO Test Purpose Why It’s Helpful Diagnosing Hashimoto’s Confirms autoimmune hypothyroidism Predicting thyroid dysfunction High risk of hypothyroidism over time Postpartum thyroid screening Identifies at-risk women Monitoring autoimmune thyroid disease Tracks antibody levels over time 🔍 Important Notes A positive result does not always mean thyroid dysfunction — some healthy individuals have antibodies without symptoms. Antibody levels can fluctuate, and high levels do not always correlate with severity. Common in: Women Family history of autoimmune disease Type 1 diabetes, celiac disease, rheumatoid arthritis ✅ Summary Feature Description Test Anti-TPO Antibodies Indicates Autoimmune attack on thyroid Common in Hashimoto’s, Graves’ disease High Levels Predict thyroid dysfunction Not Diagnostic Alone Always interpret with TSH, T4, T3

🧪 Free T4 (Thyroxine) Test The Free T4 test measures the level of unbound (free) thyroxine hormone (T4) in your blood. It is one of the most reliable tests to assess thyroid gland function and diagnose hypothyroidism or hyperthyroidism. 🧬 What Is Free T4? T4 (Thyroxine) is the main hormone produced by the thyroid gland. In the bloodstream: Most T4 is bound to proteins and inactive. Free T4 is active and enters tissues to regulate metabolism. ✅ Free T4 shows the active hormone level better than Total T4, making it more accurate for diagnosis. 📊 Normal Reference Range (May vary slightly by lab) Test Normal Range Free T4 0.8 – 1.8 ng/dL 📈 High or 📉 Low Free T4 — What It Means 📈 High Free T4 → Hyperthyroidism Overactive thyroid (e.g., Graves’ disease, thyroid nodules) Symptoms: Weight loss Palpitations Heat intolerance Anxiety, insomnia Tremors 📉 Low Free T4 → Hypothyroidism Underactive thyroid (e.g., Hashimoto’s thyroiditis) Symptoms: Fatigue Weight gain Cold intolerance Depression Constipation 🧪 When Is Free T4 Testing Important? Situation Why It Matters Abnormal TSH levels Confirms diagnosis Suspected thyroid disorder Differentiates between hypo/hyper On thyroid medication Monitors treatment effectiveness Pregnancy or pituitary issues Assesses thyroid function in complex cases 🧾 Example Lab Report Test Result Reference Range Free T4 1.6 ng/dL 0.8 – 1.8 ng/dL ✅ Interpretation: Normal Free T4 — consistent with normal thyroid function if TSH is also normal. 🔁 Should Be Interpreted With: Test Why It’s Important TSH Primary test for thyroid health Free T3 Helps assess hyperthyroidism Total T4 For evaluating protein-binding issues ✅ Summary Feature Details Hormone Free T4 (unbound thyroxine) Use Diagnosis & monitoring of thyroid disorders Normal Range ~0.8–1.8 ng/dL High Value Suggests hyperthyroidism Low Value Suggests hypothyroidism

🧪 TOTAL T3 (Triiodothyronine) & T4 (Thyroxine) Test These tests measure the total amount of thyroid hormones T3 and T4 (both bound and free) in the blood. They are used to evaluate thyroid function and help diagnose thyroid disorders such as hypothyroidism and hyperthyroidism. 🧬 What Are T3 and T4? Hormone Produced By Function T4 Thyroid gland Main hormone produced; converted to T3 in tissues T3 From T4 + thyroid More active form; regulates metabolism Most T3 and T4 in blood is protein-bound (mainly to TBG – thyroid-binding globulin). A small portion is free and biologically active. 📊 Normal Reference Ranges (May vary slightly by lab) Test Normal Range Total T3 80 – 200 ng/dL Total T4 5.0 – 12.0 µg/dL 📌 These are total levels, which include both free (active) and bound (inactive) hormone. 📉 Low or 📈 High Levels – What Do They Mean? 🟢 Normal T3 & T4 Healthy thyroid function (if TSH also normal) 📈 High T3 and/or T4 Hyperthyroidism (overactive thyroid) Symptoms: weight loss, palpitations, heat intolerance, anxiety May also occur with: Thyroiditis Overmedication with thyroid hormones 📉 Low T3 and/or T4 Hypothyroidism (underactive thyroid) Symptoms: fatigue, weight gain, cold intolerance, dry skin Could be due to: Hashimoto’s thyroiditis Iodine deficiency Pituitary dysfunction (secondary hypothyroidism) 🧪 Why Test T3 & T4 Together? Test Combo Use Total T3 + T4 General thyroid function screening With TSH Helps determine if the problem is in the thyroid or pituitary With Free T3/T4 Gives more precise picture of hormone activity With T3 Uptake or TBG To assess changes in binding proteins 🧾 Example Lab Report Test Result Reference Range Total T3 180 ng/dL 80 – 200 ng/dL Total T4 6.5 µg/dL 5.0 – 12.0 µg/dL ✅ Interpretation: T3 and T4 within normal limits, suggest normal thyroid hormone production, assuming TSH is also normal. 🧠 Summary Feature T3 T4 Type Triiodothyronine Thyroxine Tested as Total (bound + free) Total (bound + free) Used to Evaluate thyroid function Confirm thyroid status High in Hyperthyroidism Hyperthyroidism Low in Hypothyroidism Hypothyroidism

🧪 Free T3 (Triiodothyronine) Test The Free T3 test measures the unbound, biologically active form of the thyroid hormone T3 (Triiodothyronine) in your blood. It's an important test for evaluating thyroid function, especially in cases of suspected hyperthyroidism. 🧬 What Is Free T3? T3 is one of the main thyroid hormones (more active than T4). In the bloodstream: Most T3 is bound to proteins (inactive) Free T3 is unbound and active — it affects metabolism, heart rate, temperature, etc. 🧠 Free T3 reflects true hormone activity better than Total T3. 📊 Normal Reference Range (May vary slightly by lab) Test Normal Range Free T3 2.0 – 4.4 pg/mL 📈 High or 📉 Low Free T3 — What Does It Mean? 📈 High Free T3 (Hyperthyroidism) Overactive thyroid (Graves’ disease, thyroid nodules) Symptoms may include: Rapid heartbeat Anxiety, insomnia Weight loss Heat intolerance Tremors 📉 Low Free T3 (Hypothyroidism or Euthyroid Sick Syndrome) Underactive thyroid (Hashimoto’s thyroiditis, iodine deficiency) May also occur in severe illness (non-thyroidal illness syndrome) Symptoms may include: Fatigue Weight gain Cold intolerance Depression Dry skin 🧪 When Is Free T3 Especially Useful? Situation Why It’s Useful Suspected hyperthyroidism May be elevated even if T4 is normal Thyroid hormone therapy monitoring Especially with synthetic T3 medications Low TSH with normal T4 Free T3 helps clarify diagnosis Severe illness or stress May show low Free T3 (without true hypothyroidism) 🧾 Example Lab Report Test Result Reference Range Free T3 4.1 pg/mL 2.0 – 4.4 pg/mL ✅ Interpretation: High-normal Free T3 — monitor for signs of hyperthyroidism depending on TSH and Free T4. 🔁 Should Be Interpreted With: Test Purpose TSH First-line thyroid screening test Free T4 Complements Free T3 in thyroid function Total T3/T4 May help in certain binding protein disorders ✅ Summary Feature Details Hormone Triiodothyronine (T3) Form Measured Free (active, unbound) Normal Range ~2.0–4.4 pg/mL High Value Suggests hyperthyroidism Low Value Suggests hypothyroidism or illness