🦋Thyroid Test Results Explained: What TSH, T3, T4 Mean
Your doctor ordered a thyroid test but you're not sure what TSH, T3, and T4 mean? Here's a simple guide to understanding your thyroid panel results.
Dr. Sneha Reddy
Endocrinologist
Thyroid Test Results Explained: What TSH, T3, T4 Mean
"Your TSH is high" — what does that even mean? If you've been confused by your thyroid test results, you're not alone. Thyroid panels have multiple values, and they can seem contradictory.
Let's make sense of it all.
What Does the Thyroid Do?
Your thyroid is a butterfly-shaped gland in your neck. It produces hormones that control:
- Your metabolism (how fast you burn calories)
- Energy levels
- Weight
- Heart rate
- Body temperature
- Mood
When it's underactive (hypothyroidism), everything slows down. When it's overactive (hyperthyroidism), everything speeds up.
The Three Key Values
TSH (Thyroid Stimulating Hormone)
| Level | What It Means |
|---|---|
| 0.4 – 4.0 mIU/L | Normal |
| Above 4.0 mIU/L | Possible hypothyroidism |
| Below 0.4 mIU/L | Possible hyperthyroidism |
TSH is produced by your brain (pituitary gland), not the thyroid itself. It's like a thermostat:
- High TSH = your brain is yelling "Make more thyroid hormone!" because levels are low
- Low TSH = your brain is saying "Stop! We have too much!"
TSH is the most sensitive marker — it changes before T3 and T4 do.
Free T3 (Triiodothyronine)
| Level | What It Means |
|---|---|
| 2.3 – 4.2 pg/mL | Normal |
T3 is the active thyroid hormone. It's what actually does the work. Low T3 with normal TSH can still cause symptoms like fatigue and weight gain.
Free T4 (Thyroxine)
| Level | What It Means |
|---|---|
| 0.9 – 1.7 ng/dL | Normal |
T4 is the storage form. Your body converts T4 into T3 as needed. It's more stable than T3 in blood tests.
Common Patterns
| TSH | T3 | T4 | What It Suggests |
|---|---|---|---|
| High | Low/Low-normal | Low | Hypothyroidism (underactive thyroid) |
| Low | High | High | Hyperthyroidism (overactive thyroid) |
| High | Normal | Normal | Subclinical hypothyroidism |
| Normal | Normal | Normal | Normal thyroid function |
Symptoms to Watch For
Hypothyroidism (Underactive)
- Weight gain despite no diet change
- Constant tiredness
- Hair fall
- Dry skin
- Constipation
- Feeling cold when others are comfortable
- Depression
Hyperthyroidism (Overactive)
- Weight loss despite eating normally
- Rapid heartbeat
- Anxiety, nervousness
- Tremors in hands
- Heat intolerance
- Bulging eyes (in Graves' disease)
Common in Indian Women
Hypothyroidism affects 1 in 10 Indian women. Many have it without knowing. If you're experiencing unexplained weight gain, fatigue, or hair loss, get your TSH checked.
How scanura Helps
When you upload your thyroid report:
- We flag whether your TSH, T3, T4 are normal, borderline, or abnormal
- Explain what each value means in plain Hindi and English
- Generate questions like "Should I start levothyroxine?" or "How often should I retest?"
Disclaimer: This article is for educational purposes only. scanura does not provide medical diagnosis. Always consult your doctor for medical decisions.
Medical References
Step-by-Step Guide
- 1
Get a thyroid panel test
Visit a diagnostic lab for a thyroid function test. No fasting is required for TSH, T3, T4 tests.
- 2
Check TSH level
Normal range is 0.4-4.0 mIU/L. High TSH indicates possible hypothyroidism. Low TSH indicates possible hyperthyroidism.
- 3
Review Free T3
Normal range is 2.3-4.2 pg/mL. T3 is the active thyroid hormone that affects metabolism.
- 4
Check Free T4
Normal range is 0.9-1.7 ng/dL. T4 is the storage form that gets converted to T3 as needed.
- 5
Interpret the pattern
High TSH + Low T3/T4 = Hypothyroidism. Low TSH + High T3/T4 = Hyperthyroidism. High TSH + Normal T3/T4 = Subclinical hypothyroidism.
- 6
Consult an endocrinologist
If your TSH is abnormal, consult an endocrinologist. Use scanura to understand your thyroid report in plain language.