“Thyroid disease is India's hidden epidemic. I see women who have lived with fatigue and weight gain for years without knowing their thyroid was the culprit. A simple TSH test can change lives.”
— Truemark Health Editorial Team, Medically Reviewed by NABL-Certified Professionals
What Is a Thyroid Test?
A thyroid test measures how well your thyroid gland is functioning. The thyroid is a butterfly-shaped gland in your neck that produces hormones controlling metabolism, energy levels, heart rate, body temperature, and weight.
The primary thyroid test panel includes TSH (Thyroid Stimulating Hormone), Free T3 (Triiodothyronine), and Free T4 (Thyroxine). TSH is produced by the pituitary gland and tells the thyroid how much hormone to make — it is the most sensitive marker of thyroid function.
Thyroid disorders are extremely common in India. Studies estimate that about 42 million Indians suffer from thyroid disease, with women being 5–8 times more likely to be affected than men.
TSH, T3, and T4: What Each Measures
TSH (Thyroid Stimulating Hormone) is the "master controller." When thyroid hormone levels drop, the pituitary releases more TSH to stimulate the thyroid. A high TSH typically means your thyroid is underactive (hypothyroidism), while a low TSH suggests overactivity (hyperthyroidism).
Free T4 is the primary hormone produced by the thyroid gland. About 80% of thyroid output is T4, which gets converted to the more active T3 in tissues. Free T4 is the unbound, biologically available form.
Free T3 is the most metabolically active thyroid hormone. It directly affects cells throughout your body. While T3 levels can be normal even in early thyroid disease, measuring it helps your doctor understand the full picture, especially in hyperthyroidism.
Thyroid Normal Ranges by Age and Pregnancy
Thyroid reference ranges vary with age and physiological state. For non-pregnant adults, the standard TSH range is 0.4–4.0 mIU/L. However, many endocrinologists now consider 0.4–2.5 mIU/L as optimal.
During pregnancy, TSH ranges shift significantly. In the first trimester, normal TSH is 0.1–2.5 mIU/L. Second trimester: 0.2–3.0 mIU/L. Third trimester: 0.3–3.0 mIU/L. Untreated hypothyroidism during pregnancy can cause serious complications including pre-eclampsia, premature birth, and developmental delays.
For newborns, TSH can be as high as 20 mIU/L in the first few days of life. In elderly patients (over 70), a TSH up to 7.5 mIU/L may be considered acceptable without treatment.
Symptoms of Thyroid Disorders
Hypothyroidism (underactive thyroid) symptoms include unexplained weight gain, fatigue, cold intolerance, dry skin, hair loss, constipation, depression, irregular periods in women, and elevated cholesterol. Many patients dismiss these symptoms as aging or stress.
Hyperthyroidism (overactive thyroid) presents with unexpected weight loss, rapid heartbeat, anxiety, tremors, excessive sweating, heat intolerance, frequent bowel movements, and insomnia. Graves' disease is the most common cause.
Subclinical thyroid disease — where TSH is abnormal but T3/T4 remain normal — is increasingly recognized as clinically significant. It affects an estimated 10% of Indian women over 35.
When to Get Your Thyroid Tested
All adults should include a thyroid panel in their annual health checkup, especially women over 30. You should get tested immediately if you notice symptoms like unexplained weight changes, persistent fatigue, neck swelling, or menstrual irregularities.
Women planning pregnancy should get thyroid levels checked before conception. Family history of thyroid disease, autoimmune conditions (like type 1 diabetes), and a history of radiation to the head or neck are additional risk factors.
If you are already on thyroid medication (levothyroxine), regular monitoring every 6–8 weeks after dose changes and every 6 months once stable is essential to ensure optimal dosing.
Normal Range Reference Table
| Parameter | Normal Range | Unit | High Indicates | Low Indicates |
|---|---|---|---|---|
| TSH (Adults) | 0.4–4.0 | mIU/L | Hypothyroidism | Hyperthyroidism |
| TSH (1st Trimester) | 0.1–2.5 | mIU/L | Gestational hypothyroidism | Normal pregnancy suppression |
| TSH (2nd Trimester) | 0.2–3.0 | mIU/L | Hypothyroidism | Hyperthyroidism |
| TSH (3rd Trimester) | 0.3–3.0 | mIU/L | Hypothyroidism | Hyperthyroidism |
| Free T4 | 0.8–1.8 | ng/dL | Hyperthyroidism | Hypothyroidism |
| Free T3 | 2.3–4.2 | pg/mL | Hyperthyroidism (T3 thyrotoxicosis) | Severe hypothyroidism |
| Total T4 | 5.0–12.0 | μg/dL | Hyperthyroidism, pregnancy | Hypothyroidism |
| Total T3 | 80–200 | ng/dL | Hyperthyroidism | Severe illness |
TSH (Adults)
TSH (1st Trimester)
TSH (2nd Trimester)
TSH (3rd Trimester)
Free T4
Free T3
Total T4
Total T3
Frequently Asked Questions
Is fasting needed for a thyroid test?
Can thyroid problems cause weight gain?
How common are thyroid disorders in India?
What is subclinical hypothyroidism?
Can I take thyroid medication before the test?
Truemark Health Editorial Team
Medically Reviewed by NABL-Certified Professionals
The Truemark Health Editorial Team produces evidence-based health content reviewed against current clinical guidelines, ICMR standards, and peer-reviewed research. Every article is vetted for medical accuracy before publication.
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