Thyroid Profile: Understanding T3, T4 and TSH Tests
A simple guide to TSH, T3 and T4 testing, including why thyroid profiles are ordered and how results are interpreted in context.
What is a thyroid profile?
A thyroid profile is a group of blood tests used to assess thyroid function. Depending on the panel, it may include thyroid-stimulating hormone (TSH), thyroxine (T4), triiodothyronine (T3), or free forms of T3 and T4.
The thyroid gland produces hormones that influence metabolism, temperature regulation, heart rate and many other body functions.
Why are TSH, T3 and T4 measured?
TSH is produced by the pituitary gland and helps regulate thyroid hormone production. T4 is the main hormone produced by the thyroid, while T3 is a more active thyroid hormone in body tissues.
Clinicians consider these values together with symptoms, medicines, pregnancy status and other medical factors. A single result should not be interpreted in isolation.
Preparing for thyroid testing
Thyroid blood tests usually require a venous blood sample. Fasting requirements depend on the specific panel and any other tests being collected at the same time. Certain medicines and supplements can affect thyroid test interpretation, so follow your clinician’s instructions rather than stopping medicines on your own.
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