Taking up blood tests to assess your thyroid function is crucial to diagnose and treat thyroid conditions. However, it can be a bit tricky to figure the medical jargons and numbers. In this article, you learn how to interpret your thyroid tests:

How to Interpret Your Thyroid Tests

When it comes to thyroid blood test results, the thyroid function should be assessed based on the comparison of values rather than basing it on one value alone. By comparing the figures, you can assess if you have hypothyroidism or low thyroid function, hyperthyroidism or overactive thyroid function, thyroid anomalies like thyroiditis and autoimmune thyroid diseases.

Also, thyroid function is not just governed by the thyroid gland. The pituitary gland also controls it by releasing thyroid stimulating hormone or TSH. The production of TSH determines how much thyroid hormones – triiodothyronine (T3) and thyroxine (T4), are produced.

It is this inter-relationship between the three components that tell us what exactly is going on. TSH levels go in the opposite direction of your thyroid hormone levels and the relationship between these determine the right course of action.


TSH – Thyroid Stimulating Hormone

If the pituitary gland detects that there is too little thyroid hormone in the blood, it will produce more TSH in order to induce the thyroid gland to produce more. On the contrary, if it detects too much, it slows the production of TSH.

Reference Range – The normal reference range is 0.4-4.0 mU/L. Anything above the upper limit signifies hypothyroidism – underactive thyroid and anything below the lower limit signifies hyperthyroidism or overactive thyroid. If you are in the borderline, you would have to carefully watch out and wait before taking any medications.

T4 and Free T4 – Thyroxine

This functions as a storage hormone and on its, own it will not produce energy or deliver oxygen to cells. It has to convert to T3 by losing an atom of iodine through a process known as monodeiodination. The total T4 measures the total amount of thyroxine circulating in the blood but is affected by the amount of protein in the blood. While Free T4 is not affected by protein levels and is considered to be a more active form of thyroxine.

Reference Range – The normal reference range for total T4 is 4.5-12.5 µg/dL and Free T4 is 0.8-1.8 ng/dL. Several physicians base their diagnosis solely on the TSH levels. However, it should be viewed in relationship with T4 and T3.

High TSH and low total or free T4 would be considered evidence of hypothyroidism. By contrast, low levels of TSH and elevated total or free T4 levels would be considered evidence of hyperthyroidism

T3 and Free T3  – Triiodothyronine

T3 is the active thyroid hormone. The total T3 test measures the total amount of triiodothyronine circulating in the blood, both bound and unbound by protein. Only bound T3 can deliver oxygen and energy to cells. Free T3 measures only bound hormone and are considered the active form of triiodothyronine.

Reference Range – The normal reference range for total T3 is 80-200 ng/dL and free T3 is 2.3- 4.2 ng/mL. The same conditions as in T4 apply to assess conditions of hyperthyroidism and hypothyroidism.

Thyroid Antibodies – TPOAb, TSI, Tg. TgAb

The concentration of thyroid antibodies is essential to know if you suffer from other thyroid anomalies. When your immune system attacks the thyroid gland and produces too many antibodies it can lead to  Hashimoto’s disease and Graves’ disease. Similarly, low levels of antibodies may signify an inflammation of the thyroid gland or thyroiditis, type 1 diabetes or rheumatoid arthritis.

If anomalies are detected in the blood tests, further tests like Iodine Uptake Scan and Thyroid Scan can be prescribed.

As an advocate of your own health, it is very important to know about your thyroid results and where you stand. Then, by making healthy lifestyle choices, you can take the right preventive measures to maintain an optimal thyroid function.


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