Your thyroid gland produces hormones that regulate growth and energy expenditure. Thyroid disorders are quite common, and many people don’t have any symptoms at all. This thyroid test screens for the thyroid hormones that play a key role in regulating the body’s metabolism.
Communicates with the thyroid gland to produce T3 and T4 which regulate metabolic functions. High TSH thyroid test levels indicates an underactive thyroid, and low levels an overactive thyroid.
Measures the thyroxine that is freely circulating and able to regulate metabolism. High FT4 thyroid test levels indicate an overactive thyroid, and low levels an underactive thyroid.
Measures the triiodothyronine that is freely circulating. High FT3 thyroid test levels indicate an overactive thyroid, and low levels an underactive thyroid.
Reverse T3 (rT3) is virtually inactive having only 1% the activity of T3 and blocks the action of T3 acting as a metabolic break. Normal metabolism of T4 requires the appropriate balance of T3 to rT3. If the proportion of rT3 dominates then it will antagonise T3 thus producing hypothyroid symptoms despite sufficient circulating levels of T4 and T3.
Reverse T3 is an inactive form of the thyroid hormone T3. rT3 does not bind to thyroid hormone receptors and does not exert the same physiological effects. rT3 levels may be be increased during periods of stress, illness, or calorie restriction.
A higher FT3/rT3 ratio is generally associated with optimal thyroid function and metabolic activity. It suggests that the body is efficiently converting T4 into the active T3 form and that there is a lower proportion of T4 being converted into rT3.
In addition to screening for the thyroid hormones that play a key role in regulating metabolism, this advanced thyroid function test detects and measures the quantity of specific thyroid autoantibodies to determine whether autoimmune disease may be impacting thyroid function.
Thyroid peroxidase antibodies work against thyroid peroxidase, an enzyme that plays a part in the T4-to-T3 conversion and synthesis process. TPO antibodies can be evidence of tissue destruction, such as Hashimoto's disease.
When your immune system attacks the thyroid it often targets thyroglobulin which causes it to produce antithyroglobulin antibodies. Thyroglobulin antibodies are positive in about 60% of Hashimoto’s patients and 30% of Graves patients.
High levels of TSI can indicate Graves’ disease, which is an autoimmune disorder that affects the thyroid gland.
Download and print your pathology form from your i-screen dashboard.
Take your form to one of our affiliated collection centres to have your sample taken.
You do not need to fast for this blood test.