The standard thyroid test to assess thyroid health measures the amount of thyroid stimulating hormone (TSH) in your bloodstream. This thyroid hormone is produced by the pituitary gland within the brain. TSH signals the thyroid to make and release the two major thyroid hormones: thyroxine (T4) and triiodothyronine (T3). Greater quantities of TSH are released when the body requires more T4 and T3.
Could you have an underactive thyroid despite having a ‘normal’ TSH?
Testing thyroid health status is controversial. Due to restraints within the medical system the stand alone TSH test is regarded as the gold standard to check thyroid health. Individuals are often advised no further investigation is necessary when their TSH test result falls within the acceptable reference range. This can be despite the fact they are displaying the typical signs their thyroid health is well below par.
A TSH test result may appear ‘normal’ but this can be misleading and does not automatically rule out a low thyroid issue. Simply testing TSH also raises questions about what level should be considered adequate and the validity of using a wide reference range. Current research shows TSH between 0.5 and 2.0 mIU/L is ideal.
What are the top thyroid tests?
If you suspect your thyroid is underactive it is a good idea to discuss comprehensive thyroid testing with a skilled healthcare practitioner. Testing more than TSH will help reveal how well your thyroid is actually working and is useful to monitor thyroid health recovery.
It is not possible to assume the thyroid is producing adequate T4 and T3 when you only test TSH. Comprehensive testing therefore also includes an evaluation of the key thyroid hormones. Testing free T4 and T3 provides clues as to how much of these hormones are ‘free’ and available for uptake and use throughout the body. If you rely on simply testing TSH alone and do not measure these two main thyroid hormones you are missing critical parts of the puzzle.
In addition, when you assess the amount of circulating T4 and T3 in the bloodstream it provides an overall picture of how much T4 is converting to the more potent T3. For many people with a thyroid problem their bodies are not converting T4 effectively through to T3. When T3 levels rise it is usual to notice improvements in low thyroid symptoms. T3 helps stimulate metabolism which has far-reaching effects in the body including sparking energy metabolism, fat burning for weight loss and reducing thyroid hair loss.
Under normal conditions your body converts T4 to both T3 and ‘reverse T3’, which has the opposite effects of T3. The body quickly eliminates reverse T3 if it is not required to put the brakes on metabolism. Low T3 can indicate T4 is not converting effectively to T3 and may in fact be creating excess amounts of reverse T3.
Too much reverse T3 is rapidly produced when you are under enormous stress. This then leads to the common symptoms of a sluggish thyroid. Only a specific test for reverse T3 can identify high levels of this inactive form of T3. Reverse T3 dominance is diagnosed when reverse T3 remains elevated.
Evaluating thyroid antibodies levels will confirm an active thyroid autoimmune disorder. Most commonly elevated levels of thyroid antibodies are associated with Hashimoto’s thyroiditis which is a chronic inflammatory condition of the thyroid.
In summary, the top 5 thyroid blood tests I recommend to check thyroid function include; TSH, free T4, free T3, thyroid antibodies and reverse T3. When discussing thyroid blood tests with your healthcare practitioner you should also let them know if there is a family history of thyroid problems and mention your thyroid related symptoms. Low thyroid symptoms are significant indicators that your thyroid is not working well.