What is TSH?
the signal that tells your thyroid what to do
TSH is the signal from the pituitary to the thyroid. It is the most sensitive measure of thyroid function and changes early in both underactive and overactive states.
The pituitary releases TSH when thyroid hormones are low and suppresses it when they are high. The value therefore moves opposite to thyroid activity - high TSH means underactive thyroid, low TSH means overactive.
Test facts
- Unit
- mIE/L
- Sample
- Serum
- Fasting
- No fasting needed
- Turnaround
- 2 days
What does low TSH mean?
Low TSH usually means an overactive thyroid (hyperthyroidism). Symptoms can include palpitations, weight loss, heat intolerance, anxiety, and sweating.
What does high TSH mean?
High TSH suggests an underactive thyroid (hypothyroidism). Symptoms can include fatigue, weight gain, feeling cold, depression, and dry skin.
Panels that measure TSH
- Essentials
- Deep Baseline
- Female Annual
- Male Annual
- Hormone+
- Perimenopause
- Pre-Conception
- Thyroid Basic
- Thyroid Complete
- Thyroid + Autoimmune
- Stress & Cortisol Basic
- Stress & Cortisol Full
More markers in the same area
Launching in Stockholm in 2026.
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This is general information about the marker, not an assessment of your values and not medical advice. Last updated: May 2026.