BiomarkersTSH
Thyroid
TSH
The signal your brain sends to the thyroid
On your report it may say: Thyroid stimulating hormone, Thyrotropin
TSH is made by the pituitary gland to tell your thyroid how much hormone to make. A high TSH usually means the thyroid is underactive; a low TSH usually means it's overactive.
Typical ranges · µIU/mL
mIU/L is the same number
Ranges shift with age and in pregnancy, where targets are lower.
Ranges vary by lab, age and sex. The range printed on your report applies.
If it's low
Your thyroid may be overactive (hyperthyroidism), or you may be taking too much thyroid medicine.
Common causes
- Overactive thyroid
- Too much thyroid medicine
- Early pregnancy
- Biotin supplements can distort the test
What you might notice
- Weight loss
- Fast heartbeat
- Anxiety
- Feeling hot
- Tremor
If it's high
Your thyroid may be underactive (hypothyroidism), which is common in women.
Common causes
- Hashimoto's thyroiditis
- Recovery from illness
- Some medicines
- Iodine deficiency (uncommon with iodised salt)
What you might notice
- Tiredness
- Weight gain
- Feeling cold
- Constipation
- Hair thinning
Testing
- Who should test
- Anyone with tiredness, weight change, hair loss, irregular periods, or planning pregnancy.
- How to prepare
- Morning test is best; stop biotin for 2–3 days first.
- When to retest
- 6–8 weeks after any change in thyroid medicine.
What can help
SYNC doesn't recommend supplements from thyroid results. Thyroid problems need a doctor's diagnosis and treatment.
Food sources
See a doctor about any result outside the range.
Common questions
Can supplements fix my thyroid?
No. Thyroid conditions need medical treatment.
Why stop biotin before testing?
Biotin interferes with many thyroid test methods.
Explore further
Sources
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Build My Nutrition PlanFor general education only, not medical advice. Ranges shown are typical for adults; the range printed on your lab report applies. Talk to a qualified doctor about your results.