Test Details & Preparation

A thyroid panel is used to evaluate thyroid function and/or help diagnose hypothyroidism and hyperthyroidism due to various thyroid disorders. The panel typically includes tests for Thyroid-stimulating hormone (TSH), Free thyroxine (free T4) and Total or free triiodothyronine (total or free T3).

Typically, the preferred initial test for thyroid disorders is a TSH test. If the TSH level is abnormal, it will usually be followed up with a test for free T4. Sometimes a total T3 or free T3 will also be performed. Often, the laboratory will do this follow-up testing automatically. This is known as reflex testing and it saves the health practitioner time from having to wait for the results of the initial test and then requesting additional testing to confirm or clarify a diagnosis. Reflex tests are typically performed on the original sample that was submitted when the initial test was requested.

A thyroid panel may be ordered when symptoms suggest hypothyroidism or hyperthyroidism due to a condition affecting the thyroid.

Higher TSH levels mean hypothyroidism, low levels of TSH means mild hyperthyroidism or hyperthyroidism, non-thyroidal illness or secondary hypothyroidism normal TSH levels mean thyroid hormone resistance syndrome.

Normal T4 levels mean mild hyperthyroidism higher T4 levels mean thyroid hormone resistance syndrome low levels of T4 means non-thyroidal illness or secondary hypothyroidism.

Normal T3 levels mean mild hyperthyroidism higher T3 levels mean thyroid hormone resistance syndrome low levels of T3 means non-thyroidal illness or secondary hypothyroidism.

An individual person's total T4, free T4, total T3, free T3 or TSH results may vary and may be affected by changes in the proteins that bind T4 and T3 pregnancy oestrogen and other drugs liver disease systematic illness and resistance to thyroid hormones.