We carry out thyroid function tests because we know the dangers involved in hyper and hypothyroidism. If you need these tests or you want to find out more about it, feel free to call us on 020 7183 0244 for more information or booking of appointments.
Now, let’s get to know more about thyroid function tests and how we get them done.
The thyroid gland is the gland that is located below your Adam’s apple just in front of your neck. This gland has two lobes with each of them on each side of the windpipe, and they are connected by a small tissue called isthmus. This gland secretes two major hormones into your blood. The first hormone is thyroxine, which is often called T4 and contains four atoms of iodine. This hormone gets converted to tri-iodothyronine called T3 which contains three atoms of iodine.
The pituitary gland is responsible for the regulation of the amount of T4 and T3 that is secreted by the thyroid gland. This gland lies underneath the brain, and it senses the number of thyroid hormones in your bloodstream. The pituitary gland is sensitive to little drops in the level of thyroid hormones in the blood, and it secretes the thyroid-stimulating hormone (TSH) to activate the thyroid gland to secrete more of its hormones. The pituitary gland stops secreting this TSH when it senses that the amount of thyroid hormones in the blood is high. The name of this TSH is thyrotropin.
The usual thyroid function tests we carry out are TSH, T4 and sometimes T3. These tests are blood tests, and we usually take the blood from the veins and take it to our laboratory to be analysed. When we get there, we measure the free portion of T4 and T3 (FT4 and FT3). The result of these tests for a healthy adult should range from 0.4-4.0 mU/l (milliunits per litre) for TSH, 9.0-25.0 pmol/l (picomoles per litre) for FT4 and 3.5-7.8pmol/l for FT3.
These ranges of results are not the same for pregnant women.
We diagnose thyroid disorders by looking out for symptoms and by interpreting the results of the test. To find out the severity of the thyroid disorder, we may sometimes take the patients through additional tests if the results of TSH, FT4 and FT3 are not within their expected ranges. We do not advise our patients to use thyroid hormone replacement if the levels of thyroid hormones do not fall within their expected ranges.
If we realise that your TSH level is high and your FT4 level is low, it could suggest to us that you have hypothyroidism (underactive thyroid) and we recommend you get treatment for it.
If we realise your TSH is low and your FT4 is high, this would suggest hyperthyroidism (overactive thyroid) to us, and we will recommend you go for treatment.
For those whose results are a little raised but still fall within the expected end, it means you have mild thyroid failure or subclinical hypothyroidism. This condition has a tendency of developing into clinical hypothyroidism, and we usually like to undergo more tests to check for thyroid antibodies, which will help us determine the risk. Those that have subclinical hypothyroidism and find their TSH level to be greater than 10mU/l can get treated by using levothyroxine.
Failure in the pituitary gland (secondary hypothyroidism which is caused by hypopituitarism) or a response to a non-thyroid illness may result in a low TSH and FT4.
We only carry out the testing for FT3 level when we want to check for hypothyroidism or assess how severe it is.
If we realise from the result of the tests that the thyroid is dysfunctional, and we suspect it to be autoimmune thyroid disease, we usually order for the one or two thyroid antibody tests. Some thyroid antibodies are thyroglobulin antibodies (TgAb), thyroid peroxidase antibodies (TPOAb), and thyroid-stimulating hormone receptor antibodies (TSHR Ab or TRAb). We do not use the standard reference range for thyroid antibodies because it is dependent on many factors.
Some tests are more specialised. They are thyroglobulin (Tg) which is used to monitor people that have been treated for a different type of thyroid cancer) and the calcitonin, which is used to monitor people that have medullary thyroid cancer.
The treatments that are given are to make you feel better and prevent you from being affected by the long-term effects of thyroid hormone replacement. The most sensitive marker of the status of your thyroid, which is the blood test for TSH is used to ensure that the replacement of your thyroid hormone is adequate.
We recommend that patients who have undergone hormone replacement should strive to ensure their TSH does not go out of the normal range.
When over-replacement of the thyroid hormone is done (i.e. the TSH can no longer be detected), they may be an effect causing osteoporosis and may cause the cardiovascular system to be affected after some time. We usually use a different approach when we are targeting thyroid cancer because the aim will be to keep the level of the TSH on the lower part of the normal range.
During our work, we have met patients who feel better only if their TSH is suppressed or below the normal. This does not pose any risk provided the TSH level is still detectable, and the FT3 is still normal. We have also met patients who only feel better when their TSH is slightly above the normal range. In cases like this, we usually advise the patients.
Those with hypothyroidism will not need to get the TSH test frequently, having it done once in a year is okay while those with hyperthyroidism will need more frequent tests for FT4 and FT3 depending on the treatment.
Your doctor may ask you to go for additional tests if your results are abnormal. If this is your case, do not panic, just come to us, and we will help you get tested easily.
The results of these tests may be influenced by the medications you use or illness. We usually appreciate it if patients tell us about anything they know that may affect the result of their tests. These common factors are:
You can meet with us and ask if you should have a blood test if:
Other reasons that should prompt you to get a thyroid function test if you
We usually advise the following people to get tested for thyroid function at least once a year or more frequently at your doctor’s advice:
We also advise people with Turner syndrome, Down’s syndrome and Addison’s disease or other autoimmune diseases to get regularly tested.
If you need to carry out these tests or any other tests, come to us, we will be expecting you. We are qualified to carry out any test you want us to and provide you with accurate results.
Call us now on
020 71830244! to book an appointment or visit us here or at
Suite E, 117a Harley St, Marylebone, London W1G 6AT.