🦋 Thyroid Function Test Interpretation
Interpret common TSH/FT4/FT3 combinations — primary, subclinical, central and sick-euthyroid disease, with pregnancy caveats. Browser-side reference.
Read TSH first, then the FT4 combination.
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When to use
Read thyroid function by combination, starting with TSH then FT4. Avoid testing in critical illness.
How it works
TSH ↑ FT4 ↓ primary hypothyroid; TSH ↑ FT4 normal subclinical; TSH ↓ FT4/FT3 ↑ hyperthyroid; TSH ↓ FT4 ↓ central/sick-euthyroid.
Key points
- Read TSH first, then the FT4 combination.
- Follow central disease by FT4, not TSH.
- Sick-euthyroid (low-T3) is easily misread in critical illness.
- Use trimester-specific reference ranges in pregnancy.
References
Worked calculation
The values below come from this tool's own example placeholders and are computed server-side with the formula shown on this page, so the arithmetic can be checked quickly. It demonstrates how to substitute values only — it is not clinical advice and not a real case.
| View | Common combinations |
|---|
→InterpretationCommon combinations
- TSH ↑ FT4 ↓：Primary hypothyroidism
- TSH ↑ FT4 normal：Subclinical hypothyroidism
- TSH ↓ FT4/FT3 ↑：Hyperthyroidism (primary)
| View | Pregnancy |
|---|
→InterpretationPregnancy
- Reference ranges：TSH range shifts down; hCG lowers first-trimester TSH
- Cue：Interpret against trimester-specific reference ranges
Frequently asked questions
- What is Thyroid Function Test Interpretation?
- Interpret common TSH/FT4/FT3 combinations — primary, subclinical, central and sick-euthyroid disease, with pregnancy caveats. Browser-side reference.
- How is Thyroid Function Test Interpretation calculated? What is the core formula?
- TSH ↑ FT4 ↓ primary hypothyroid; TSH ↑ FT4 normal subclinical; TSH ↓ FT4/FT3 ↑ hyperthyroid; TSH ↓ FT4 ↓ central/sick-euthyroid.
- When is Thyroid Function Test Interpretation used?
- Read thyroid function by combination, starting with TSH then FT4. Avoid testing in critical illness.
- What are the key clinical points for Thyroid Function Test Interpretation?
- Read TSH first, then the FT4 combination. Follow central disease by FT4, not TSH. Sick-euthyroid (low-T3) is easily misread in critical illness. Use trimester-specific reference ranges in pregnancy.
- What are the limits and cautions when using Thyroid Function Test Interpretation?
- For licensed clinicians and clinical researchers. Interpret results with history, investigations and local protocols; not a diagnosis or prescription, and not a substitute for multidisciplinary decision-making or local guidelines.
- How is Thyroid Function Test Interpretation calculated in practice? Can you show a worked example?
- Inputs: View Common combinations → Result: Interpretation Common combinations（TSH ↑ FT4 ↓: Primary hypothyroidism, TSH ↑ FT4 normal: Subclinical hypothyroidism, TSH ↓ FT4/FT3 ↑: Hyperthyroidism (primary)） Inputs: View Pregnancy → Result: Interpretation Pregnancy（Reference ranges: TSH range shifts down; hCG lowers first-trimester TSH, Cue: Interpret against trimester-specific reference ranges）