Indicator Explainer
TSH
Thyroid-stimulating hormone — the pituitary signal that regulates the thyroid and the usual first test of thyroid function.
This page explains what the indicator is and how results are interpreted in general terms. Reference ranges depend on the laboratory, the method, and your own situation — no single “normal value” applies to everyone. This page is health information, not a diagnosis. For symptoms, treatment, or urgent concerns, contact a healthcare professional.
When it is tested
Measured when thyroid disease is suspected, for periodic monitoring of thyroxine replacement or antithyroid drugs, and in many antenatal screening pathways.
Reading results
TSH varies with time of day, acute illness, and several medications; recovery from illness can transiently distort it. Interpretation differs in pregnancy, pituitary disease, and in patients on specific supplements (biotin can interfere with some immunoassays). Each laboratory’s reference interval reflects its assay; a mildly abnormal value often needs repeat confirmation before treatment decisions.
Questions to ask a professional
- When was the sample taken, and were any biotin supplements or thyroid medications in use?
- Is this result stable across repeat testing?
- Does pregnancy or known pituitary disease change the expected range here?