ABOUT THIS TEST
ROYAL MAIL TRACKED 24 SAMPLE RETURN INCLUDED
What are the thyroid tests and why are they important?
The thyroid tests are used to evaluate the function of the thyroid gland; to help diagnose thyroid gland disorders. The thyroid hormones regulate the body’s metabolism and how it grows, functions and uses energy
The thyroid gland is located at the front of the neck. It secretes two hormones known as thyroxine (T4) and tri-iodothyronine (T3) . The release of T4 and T3 into the blood is controlled by a third hormone called thyroid stimulating hormone (TSH), this hormone is responsible for keeping FT4 and FT3 at the right levels. Collectively, these three hormones are referred to as ‘thyroid function tests’ (TFTs).
There are two main conditions the effect the thyroid
- Hypothyroidism (know as underactive thyroid) is when the thyroid glands fails to produce sufficient hormones for health. This can be treated by thyroid hormone replacement.
- Hyperthyroidism (known as overactive thyroid) is when the thyroid gland produces too much thyroid hormone. This can be treated by hospital specialist depending on the cause.
Please note: these tests are available for people aged over 18 only. Please collect and post your sample to us Monday-Thursday, to avoid delays over the weekend. In a small number of cases, it may not always be possible to provide a result, please see our terms and conditions for details.
Who is this test for?
People who may benefit from having a thyroid function test include:
Individuals who are concerned that they may have a thyroid problem and those who wish to monitor a previously diagnosed condition.
Early signs and symptoms of thyroid dysfunction may often be very non-specific. The common symptoms hypothyroidism may include:
- Unexplained weight gain
- Dry skin
- Feeling cold
- Puffy skin
- Hair loss
- Tiredness
Some signs and symptoms of hyperthyroidism may include:
- Fast heart rate
- Anxiety
- Unexplained weight loss
- Feeling hot
- Hand tremors
- Bulging, dry, puffy or irritated eyes
- Difficulty sleeping (insomnia)
What will the result show?
Our thyroid test includes measurement of TSH (also known as thyroid stimulating hormone), free T4 (also known as free thyroxine or FT4) and free T3 (also known as free triiodothyronine or FT3). These three tests are nationally recommended for assessment of thyroid function. Our thyroid test will report your levels for all three hormones. You will receive a personalised interpretation of what the results mean and what you should do about them. This may be as simple as; all is well, to a recommendation to see your GP if we detect an abnormality.
In hypothyroidism, the thyroid gland does not produce sufficient thyroxine, so the T4 and T3 levels are low.
This causes an increase in TSH to try and stimulate the thyroid to produce more thyroxine.
In hyperthyroidism the thyroid gland produces too much thyroxine, so the T4 levels are high. This causes a decrease in TSH to try and stop the thyroid producing more thyroxine.
Recent illness or infection
Being unwell can impact thyroid test results. We would recommend waiting 3 to 4 weeks after recovering from illness or infection before doing our thyroid tests.
There is no need to stop taking thyroid medication before doing this test. It will not change the accuracy of the test.
Supplements that contain biotin (also known as vitamin B7) can sometimes affect thyroid testing. We recommend leaving the following amount of time between biotin supplement and our blood test:
Less than 10,000 mcg/day (10 mg/day) of biotin – 24 hours
10,000 mcg/day or above (10 mg/day or above) of biotin – 72 hours
Interpretation of thyroid tests
We provide comments to help you understand your thyroid results and to tell you when we think you should see your doctor. Our comments only apply to people who have not been diagnosed with a thyroid condition and are not on thyroid medication. This is because the monitoring of thyroid disorders needs to look at results together with how you are feeling e.g. ongoing symptoms. For this reason, we are unable to give advice about treatments or the amount you are taking.
Ticking the "taking thyroid medication" box does not change how we process or analyse the sample. It also does not change the normal ranges we provide. It will just stop us from providing a comment with the result that would likely not be relevant to your individual treatment.
Results in the normal range
If you have not been previously diagnosed with a thyroid condition and all three of your thyroid test results are within the normal range, then it is very unlikely that you have a thyroid condition. This is the case even if one or more of your results is close to the top or bottom of the range.
Thyroid disorders tend to produce distinct patterns with changes in all three hormones that we measure. For example, with an underactive thyroid the TSH usually goes up and both FT4 and FT3 go down. Occasionally, we see results that do not fit with these patterns and there can be several reasons for this:
- Medication or recent illness can influence thyroid tests and lead to unusual patterns.
- A result may be a little outside of the normal range and still be normal for you. Our normal ranges are designed so that results from 95% of healthy people will fall inside the range. This means that 5% of healthy people (1 in 20 people) will have a result outside of the normal range but this will be perfectly normal for them. If your FT4 or FT3 result is just outside of the normal range and the other two thyroid results are within range then this could apply to you.
- There are some rare conditions that can lead to unusual thyroid patterns. If you have symptoms that you feel may be related to a thyroid problem and an unusual thyroid pattern then we would suggest seeing your GP to discuss your results.
Thyroid Stimulating Hormone (TSH) - Roche Cobas Elecsys TSH electrochemiluminescence immunoassay
Thyroxine (T4, free direct) - Roche Cobas Elecsys FT4 III electrochemiluminescence immunoassay
Triiodothyronine (T3, free) - Roche Cobas Elecsys FT3 III electrochemiluminescence immunoassay
Thyroid peroxidase antibodies – Roche Cobas Elecsys Anti-TPO electrochemiluminescence immunoassay
All four tests are analysed on a Roche Cobas e801 analyser
The ranges are represented visually on the chart so you can see exactly where your result lies in relation to the ranges.
The ranges are:
TSH 0.27 to 4.20 mIU/L
FT4 12.0 to 22.0 pmol/L
FT3 3.1 to 6.8 pmol/L
