Thyroid Profile
TSH is the pituitary’s instruction to the thyroid, and it moves in the OPPOSITE direction to thyroid activity: an underactive thyroid produces a high TSH, an overactive one a low TSH. That inversion is what makes thyroid results feel back-to-front the first time you read them.
This is an educational reading aid, not a diagnosis and not medical advice. Reference ranges differ between laboratories — always read the range printed on your own report. Nothing here can see you, your history or your medicines. Do not start, stop or change any treatment on the strength of this page: take your report to a qualified doctor.
Reference ranges reviewed by Dr. Mohan Gayenlast reviewed
Your values
Fill in only the ones on your report. Anything you leave blank is simply skipped.
The pituitary hormone that tells the thyroid to work. It moves opposite to thyroid activity.
The active, unbound form of the main thyroid hormone.
The most active thyroid hormone. It often falls last in underactivity and rises first in overactivity.
Enter one or more values and your reading will appear here.
Reading the pattern, not the numbers
What a combination of TSH and free T4 usually indicates. Every one of these needs a doctor to confirm and to find the cause.
| TSH | Free T4 | Usual interpretation |
|---|---|---|
| High | Low | Primary hypothyroidism — an underactive thyroid gland |
| High | Normal | Subclinical hypothyroidism — often monitored rather than treated straight away |
| Low | High | Hyperthyroidism — an overactive thyroid gland |
| Low | Normal | Subclinical hyperthyroidism — needs assessment; also seen with too much thyroid medication |
| Low | Low | Suggests a pituitary cause, or recovery from a severe illness — needs specialist assessment |
| Normal | Normal | Thyroid function is normal |
| High | High | An uncommon pattern — assay interference, poor adherence to medication, or rare pituitary causes |
What this panel is easy to get wrong
- PREGNANCY HAS ITS OWN RANGES, trimester by trimester. Do not read a pregnancy result against these bands.
- TSH is not interpretable during or soon after an acute illness, and biotin supplements can distort thyroid immunoassays badly — stop biotin for a few days before the test if your doctor agrees.
- A single abnormal TSH is usually repeated with free T4 before anything is concluded or started.
Where these ranges come from: Commonly published adult intervals. TSH intervals vary between laboratories and assays more than most tests; pregnancy uses different, trimester-specific ranges.
Where this is written from: This site is written from Indian clinical practice. Drug availability and brand names, vaccination schedules, national health programmes and some reference cut-offs differ between countries — a schedule or a threshold that is standard here may not be standard where you are. If you are reading outside India, check anything on this page against your own country’s guidance before you act on it.
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TSH, free T4 and free T3 — and the patterns they make together.