🦋 Adult Hypothyroidism: Starting Levothyroxine
UseUse to decide whether to replace and how to start: overt and central hypothyroidism need replacement, subclin…
SourceJonklaas J, et al. Guidelines for the Treatment of Hypothyroidism. Thyroid 2014 (ATA).
This-shift next steps
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Methodology · worked example, guidelines & full notes
In central hypothyroidism, adrenocortical insufficiency must be assessed and corrected before levothyroxine to avoid precipitating adrenal crisis, and monitoring uses FT4 rather than TSH. (original synthesis · not guideline verbatim)
When to use
Use to decide whether to replace and how to start: overt and central hypothyroidism need replacement, subclinical disease is treated at TSH ≥ 10 or with high-risk features, and starting dose is tailored to age/cardiac status and pregnancy.
How it works
Overt/central → replace (central: assess adrenal function first, monitor FT4). Subclinical: TSH ≥ 10 → treat; TSH < 10 with pregnancy/symptoms/TPOAb/CV risk → consider. Full dose about 1.6 μg/kg/d (adjusted in older/cardiac patients and pregnancy per current guidelines).
Key points
- In central hypothyroidism, adrenocortical insufficiency must be assessed and corrected before levothyroxine to avoid precipitating adrenal crisis, and monitoring uses FT4 rather than TSH. (original synthesis · not guideline verbatim)
- Older patients or those with ischemic heart disease start low and uptitrate slowly.
- Pregnancy requires prompt full replacement with a higher dose and trimester-specific TSH targets.
References
- [Guideline / primary source]Jonklaas J, et al. Guidelines for the Treatment of Hypothyroidism. Thyroid 2014 (ATA).
- [Guideline / primary source]Chinese Society of Endocrinology. Guideline for the diagnosis and management of adult hypothyroidism.
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.
| Hypothyroidism type | Subclinical hypothyroidism (TSH↑, FT4 normal) |
|---|---|
| TSH (for subclinical, mU/L) | 8 mU/L |
| Marked symptoms / positive TPOAb / planning pregnancy / dyslipidemia etc. | Present |
| Age > 50 yr or ischemic heart disease | Yes |
| Pregnancy | Yes |
| Weight (optional, for dose estimate) | 60 kg |
→DispositionConsider LT4 replacement
- Decision：Subclinical hypothyroidism, TSH < 10, but with pregnancy/planning pregnancy, marked symptoms, positive TPOAb, or high cardiovascular risk: treatment may be considered.
- Starting strategy：Pregnancy: start at full replacement dose and reach target promptly; the dose is higher than non-pregnant, adjusted to trimester-specific TSH targets.
- Dose estimate：Full replacement dose about 1.6 μg/kg/d (titrate by thyroid function; other doses per current guidelines and local protocols)
| Hypothyroidism type | Overt hypothyroidism (TSH↑ + FT4↓) |
|---|---|
| TSH (for subclinical, mU/L) | 8 mU/L |
| Marked symptoms / positive TPOAb / planning pregnancy / dyslipidemia etc. | Present |
| Age > 50 yr or ischemic heart disease | Yes |
| Pregnancy | Yes |
| Weight (optional, for dose estimate) | 60 kg |
→DispositionRecommend LT4 replacement therapy
- Decision：Overt hypothyroidism (elevated TSH + low FT4) needs replacement, usually lifelong.
- Starting strategy：Pregnancy: start at full replacement dose and reach target promptly; the dose is higher than non-pregnant, adjusted to trimester-specific TSH targets.
- Dose estimate：Full replacement dose about 1.6 μg/kg/d (titrate by thyroid function; other doses per current guidelines and local protocols)
Verification & sources · governance
FAQ
Frequently asked questions
- What are the limits and cautions when using Adult Hypothyroidism: Starting Levothyroxine?
- 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.
- Does Adult Hypothyroidism: Starting Levothyroxine upload patient data? Where is it calculated?
- Calculation runs locally in the browser; inputs and results are not uploaded. For licensed clinicians only; interpret with history, investigations and local protocols — not a diagnosis or prescription.
- How is Adult Hypothyroidism: Starting Levothyroxine calculated in practice? Can you show a worked example?
- Inputs: Hypothyroidism type Subclinical hypothyroidism (TSH↑, FT4 normal), TSH (for subclinical, mU/L) 8 mU/L, Marked symptoms / positive TPOAb / planning pregnancy / dyslipidemia etc. Present, Age > 50 yr or ischemic heart disease Yes, Pregnancy Yes, Weight (optional, for dose estimate) 60 kg → Result: Disposition Consider LT4 replacement（Decision: Subclinical hypothyroidism, TSH < 10, but with pregnancy/planning pregnancy, marked symptoms, positive TPOAb, or high cardiovascular risk: treatment may be considered., Starting strategy: Pregnancy: start at full replacement dose and reach target promptly; the dose is higher than non-pregnant, adjusted to trimester-specific TSH targets., Dose estimate: Full replacement dose about 1.6 μg/kg/d (titrate by thyroid function; other doses per current guidelines and local protocols)） Inputs: Hypothyroidism type Overt hypothyroidism (TSH↑ + FT4↓), TSH (for subclinical, mU/L) 8 mU/L, Marked symptoms / positive TPOAb / planning pregnancy / dyslipidemia etc. Present, Age > 50 yr or ischemic heart disease Yes, Pregnancy Yes, Weight (optional, for dose estimate) 60 kg → Result: Disposition Recommend LT4 replacement therapy（Decision: Overt hypothyroidism (elevated TSH + low FT4) needs replacement, usually lifelong., Starting strategy: Pregnancy: start at full replacement dose and reach target promptly; the dose is higher than non-pregnant, adjusted to trimester-specific TSH targets., Dose estimate: Full replacement dose about 1.6 μg/kg/d (titrate by thyroid function; other doses per current guidelines and local protocols)）