Thyroid Stimulating Hormone (TSH)
Disclaimer: Information on this page is for educational purposes. Consult a physician to interpret your test results. Lissa Health helps track biomarker trends but does not replace medical advice.
What This Test Measures
TSH is the pituitary hormone stimulating the thyroid. The most sensitive screening test for thyroid dysfunction.
Elevated TSH with normal/low T4 indicates primary hypothyroidism. Low TSH with high T4/T3 indicates hyperthyroidism.
Target TSH on levothyroxine is usually 0.5–2.5 mIU/L (individualized).
Normal Ranges
| Group | Reference Range |
|---|---|
| Men | 0.4–4.0 mIU/L |
| Women | 0.4–4.0 mIU/L |
| Children | 0.7–6.4 mIU/L (age-dependent) |
Reference ranges may vary by laboratory and assay method.
Causes of High Levels
- Primary hypothyroidism
- Hashimoto thyroiditis
- Post-thyroidectomy
- Iodine deficiency
- TSH-secreting pituitary adenoma (rare)
Causes of Low Levels
- Hyperthyroidism (Graves disease, toxic nodule)
- Excess levothyroxine
- Secondary hypothyroidism (pituitary)
- Critical illness (sick euthyroid syndrome)
Test Preparation
- Morning draw (TSH has diurnal rhythm)
- Report levothyroxine (test before dose)
- Stable iodine intake
Related Biomarkers
| Biomarker | Relationship |
|---|---|
| Free Thyroxine (T4) | Thyroid function |
| Free Triiodothyronine (T3) | Active hormone |
| Total Cholesterol | Metabolic effects |
FAQ
How often should I take this test?
Annually after age 35; on levothyroxine — every 6–8 weeks during titration, then 6–12 months.
What should I do if my result is abnormal?
Abnormal TSH — full thyroid panel and endocrinology consult.
Last updated: June 2026