Why Thyroid Testing Matters
Thyroid disorders affect 1 in 10 Indians — women are 5–8× more likely to be affected. Hypothyroidism (underactive) and hyperthyroidism (overactive) have vastly different symptoms but both significantly impact quality of life and — if untreated — can cause serious cardiac, bone, and metabolic problems.
The Key Tests
TSH (Thyroid Stimulating Hormone) — the MOST IMPORTANT screening test
Produced by pituitary gland to stimulate thyroid. Normal: 0.4–4.0 mIU/L (lab-specific ranges vary). High TSH → thyroid underactive → HYPOTHYROIDISM. Low TSH → thyroid overactive → HYPERTHYROIDISM. TSH alone is sufficient to screen for thyroid disease in most cases.
Free T4 (FT4)
The main hormone secreted by the thyroid. Normal: 12–22 pmol/L. Confirmed LOW FT4 + HIGH TSH = Primary hypothyroidism. Confirmed HIGH FT4 + LOW TSH = Hyperthyroidism.
Free T3 (FT3)
Active form of thyroid hormone (T4 converts to T3 in tissues). Less useful for routine screening; helpful for T3 toxicosis and monitoring hyperthyroid treatment.
Thyroid Antibodies
- Anti-TPO antibodies: marker of Hashimoto's thyroiditis (commonest cause of hypothyroidism)
- TSH receptor antibodies (TRAb): Graves' disease (commonest cause of hyperthyroidism)
FAQ
Do I need to fast for thyroid tests? No fasting is required for TSH, FT4 or FT3. However, biotin supplements (found in hair/nail supplements) can interfere — tell your clinician and laboratory if you take biotin and follow their instructions before testing.
My TSH is slightly high — do I need medication? Subclinical hypothyroidism (mildly elevated TSH with normal FT4) in otherwise well patients is often monitored rather than treated immediately. Treatment is generally recommended if TSH >10, or if symptomatic, pregnant, or trying to conceive.