Test guide
Thyroid Stimulating Hormone (TSH)
The pituitary hormone that regulates the thyroid; the primary first-line test for thyroid dysfunction.
What it is for
Screens for thyroid dysfunction, monitors thyroxine replacement or antithyroid therapy, and investigates symptoms ranging from fatigue to menstrual irregularity. In most settings a normal TSH with a compatible clinical picture excludes primary thyroid disease.
Limitations
Values vary with time of day, acute illness, and certain medications (biotin supplements can interfere with some immunoassays). Pituitary disease and pregnancy alter the expected range. Interpretation requires the clinical context; TSH alone does not characterise thyroid status in all situations.
Before you test
Morning sampling is commonly preferred. Mention biotin or thyroid medication use before testing.
Health information only. This guide does not diagnose or replace advice from a healthcare professional.
Also known as
- TSH
- thyrotropin
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