The thyroid function test (TFT), commonly known as the thyroid profile test, is an essential diagnostic tool to assess the health of the thyroid gland. The thyroid gland plays a crucial role in regulating metabolism, energy levels, and various bodily functions. In this article, we will explore the thyroid function test, its normal values, cost, and report interpretation, providing an in-depth learning experience with Dr. Anirban Biswas.
What is a Thyroid Function Test?
A thyroid function test (TFT) measures the levels of thyroid hormones in the blood, primarily Thyroid-Stimulating Hormone (TSH), Triiodothyronine (T3), and Thyroxine (T4). It helps diagnose conditions like hypothyroidism (underactive thyroid) and hyperthyroidism (overactive thyroid).
Many people search for thyroid profile test in Hindi, wondering about its significance. Simply put, this test evaluates how well your thyroid gland is functioning.
Thyroid Function Test Name Includes:
A thyroid function test blood test typically includes:
TSH (Thyroid-Stimulating Hormone) – Regulates the production of T3 and T4.
Free T4 (Thyroxine) – The active form of T4 in the bloodstream.
Total T4 and Total T3 – Measures bound and unbound thyroid hormones.
Free T3 (Triiodothyronine) – The active hormone affecting metabolism.
Thyroid Antibodies – Includes anti-TPO (Thyroid Peroxidase Antibodies) and TgAb (Thyroglobulin Antibodies), useful in diagnosing autoimmune thyroid disorders like Hashimoto’s thyroiditis or Graves' disease.
Many diagnostic centers mention the thyroid profile test includes these parameters when listing the test details.
Constituents of a Thyroid Profile Test
Thyroid-Stimulating Hormone (TSH)
Function: TSH is secreted by the pituitary gland to stimulate the thyroid gland to produce thyroid hormones (T3 and T4).
Normal Range:
Adults: 0.4–4.0 mIU/L (may vary slightly by lab).
Significance:
High TSH: Indicates hypothyroidism (underactive thyroid) if T3 and T4 are low. If T3 and T4 are high, it could suggest a pituitary issue.
Low TSH: Indicates hyperthyroidism (overactive thyroid) or pituitary dysfunction.
Total Thyroxine (T4)
Function: T4 is the primary hormone produced by the thyroid gland, later converted to T3 in the body.
Normal Range:
Total T4: 5.0–12.0 µg/dL.
Free T4: 0.8–2.0 ng/dL.
Significance:
High T4: Hyperthyroidism, thyroiditis, or excess iodine intake.
Low T4: Hypothyroidism, iodine deficiency, or chronic illness.
Triiodothyronine (T3)
Function: T3 is the active form of thyroid hormone and is responsible for most thyroid-related metabolic effects.
Normal Range:
Total T3: 80–200 ng/dL.
Free T3: 2.3–4.2 pg/mL.
Significance:
High T3: Indicates hyperthyroidism or excessive supplementation of thyroid hormones.
Low T3: Associated with hypothyroidism or a non-thyroidal illness.
Free Thyroxine Index (FTI)
Function: An estimation of free T4 levels, derived from total T4 and T3 uptake.
Normal Range: 1.0–4.0 units.
Significance:
A helpful adjunct to distinguish between euthyroid and thyroid dysfunction states.
Thyroid Antibodies
Includes Anti-thyroid peroxidase (TPOAb) and Thyroglobulin antibodies (TgAb).
Function: Assess autoimmune causes of thyroid dysfunction (e.g., Hashimoto’s thyroiditis or Graves’ disease).
Normal Range:
TPOAb: <35 IU/mL.
TgAb: <20 IU/mL.
Significance:
High levels suggest autoimmune thyroid disease.
Reverse T3 (rT3) (Optional)
Function: An inactive form of T3 that helps assess the thyroid's role in critical illnesses.
Normal Range: 90–350 pg/mL.
Significance:
Elevated in non-thyroidal illness or stress.
Thyroid Function Test Report Interpretation
A. Normal Thyroid Function (Euthyroid)
TSH, T3, and T4 are within normal limits.
B. Hypothyroidism
Primary Hypothyroidism:
High TSH, low T3/T4.
Subclinical Hypothyroidism:
Slightly elevated TSH with normal T3/T4.
Causes:
Hashimoto’s thyroiditis, iodine deficiency, or certain medications.
C. Hyperthyroidism
Primary Hyperthyroidism:
Low TSH, high T3/T4.
Subclinical Hyperthyroidism:
Low TSH with normal T3/T4.
Causes:
Graves’ disease, toxic multinodular goiter, or excess iodine.
D. Non-Thyroidal Illness Syndrome (Euthyroid Sick Syndrome)
Low T3, normal or low T4, and normal TSH due to critical illness, not intrinsic thyroid dysfunction.
Table 1. Clinical Significance of Abnormal Thyroid Profiles
Test | Normal Range | High Reading Implications | Low Reading Implications |
|---|---|---|---|
TSH | 0.4–4.0 mIU/L | Hypothyroidism, pituitary adenoma | Hyperthyroidism, pituitary insufficiency |
T4 (Free/Total) | Free: 0.8–2.0 ng/dL Total: 5.0–12.0 µg/dL | Hyperthyroidism, thyroiditis | Hypothyroidism, iodine deficiency |
T3 (Free/Total) | Free: 2.3–4.2 pg/mL Total: 80–200 ng/dL | Hyperthyroidism, T3 thyrotoxicosis | Hypothyroidism, non-thyroidal illness |
TPOAb | <35 IU/mL | Autoimmune thyroiditis (e.g., Hashimoto’s) | Not clinically significant |
TgAb | <20 IU/mL | Autoimmune thyroid disorders | Not clinically significant |
Factors Influencing Thyroid Test Results
Medications: Amiodarone, lithium, and steroids can affect readings.
Pregnancy: Alters TSH and thyroid hormone levels.
Iodine Intake: Excess or deficiency impacts T3/T4 production.
Stress and Illness: Can alter T3 and rT3 levels.
When to Get a Thyroid Profile Test?
Symptoms of thyroid dysfunction:
Hypothyroidism: Fatigue, weight gain, hair loss, cold intolerance, constipation.
Hyperthyroidism: Weight loss, heat intolerance, palpitations, anxiety, tremors.
Routine screening for:
Women over 35.
Pregnant women.
Family history of thyroid disease.
Thyroid Function Test Cost in India
One of the most frequently asked questions is, "What is the cost of thyroid function test?" The thyroid function test price varies depending on the lab and city.
Average cost of thyroid function test: ₹200–₹800
Thyroid profile test price Lal Pathlabs: ₹700–₹900 (depending on location)
Home thyroid function test: ₹500–₹1,000 (including sample collection)
People often search for thyroid profile test price Lal Pathlabs, as it is one of India's leading diagnostic chains.
Where to Get a Thyroid Function Test?
A thyroid function test blood test can be done at hospitals, diagnostic labs, or even as a home thyroid function test, where a phlebotomist collects the blood sample from your home.
For those wondering about thyroid function test name when booking a test, look for:
Thyroid Profile Test
TFT (Thyroid Function Test)
Complete Thyroid Panel
Conclusion
The thyroid function test is an essential diagnostic tool for detecting thyroid disorders early. Understanding thyroid function test normal value, interpreting the thyroid function test report, and knowing the cost of thyroid profile test can help you take proactive steps in managing thyroid health.
If you have symptoms of thyroid imbalance, consult a specialist like Dr. Anirban Biswas for expert guidance on diagnosis and treatment.
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