A blood sample taken from a vein in your arm
These tests detect the presence and measure the quantity of specific thyroid autoantibodies in the blood. These autoantibodies develop when a person’s immune system mistakenly recognises components of the thyroid gland or thyroid proteins as foreign (non-self) and can lead to chronic inflammation of the thyroid (thyroiditis), tissue damage, and disruption of thyroid function.
The thyroid is a small, butterfly-shaped gland that lies flat against the windpipe in the throat. The primary hormones that it produces (thyroxine (T4) and triiodothyronine (T3)) are vital in helping to regulate the rate at which we use energy. The body has a feedback system that utilises thyroid stimulating hormone (TSH) to help turn thyroid hormone production on and off and maintain a stable amount of the thyroid hormones in the bloodstream. When thyroid antibodies interfere with this process, it can lead to chronic conditions and disorders associated with hypothyroidism (not enough thyroid hormones) or hyperthyroidism (excessive amounts of thyroid hormones). Hypothyroidism can cause symptoms such as weight gain, fatigue, goitre (enlarged thyroid gland), dry skin, hair loss, intolerance to cold, and constipation. Hyperthyroidism can cause symptoms such as sweating, rapid heart rate, anxiety, tremors, fatigue, difficulty sleeping, sudden weight loss, and protruding eyes.
How is the sample collected for testing?
A blood sample is obtained after inserting a needle with syringe into a vein in the arm.
Is any test preparation needed to ensure the quality of the sample?
No test preparation is needed.
How is it used?
Thyroid antibody testing may be used to help investigate the cause of an enlarged thyroid gland (goitre) and/or performed as a follow-up when other thyroid test results (such as free T3, free T4, and/or TSH) show signs of thyroid dysfunction. Antibody testing is primarily requested to help diagnose an autoimmune thyroid disease and to separate it from other forms of thyroiditis and thyroid disease.
Thyroid antibody tests may also be requested if a person with a known non-thyroid-related autoimmune condition, such as systemic lupus erythematosus (SLE), rheumatoid arthritis, or pernicious anaemia, develops symptoms that suggest thyroid involvement. This involvement may occur at any time during the course of the other condition(s).
When is it requested?
Thyroid Antibody Acronym Present in When ordered Thyroid peroxidase antibody/thyroid microsomal antibody TPOAb Autoimmune thyroid disease: Hashimoto’s thyroiditis (95%); primary myxoedema (90%); Graves’ disease (18%) When patient has symptoms or test results suggesting hypothyroidism; when a doctor is considering starting a patient on a drug therapy, such as lithium, amiodarone, interferon alpha, or interleukin-2, that has associated risks of developing hypothyroidism when TPOAb are present Thyroglobulin antibody TgAb Tested as part of monitoring of treatment for thyroid cancer. Also present in autoimmune thyroid disease. Not as reliable as TPOAb in testing for autoimmune thyroid disease. Thyroglobulin antibody together with thyroglobulin levels are used at regular intervals after thyroid cancer treatment. The presence of thyroglobulin antibodies may interfere with the test for thyroglobulin which is also tested as a tumour marker. Thyroid stimulating hormone receptor antibody TRAb Graves’ disease When patient has symptoms of hyperthyroidism; to monitor effectiveness of anti-thyroid therapy
If a pregnant woman has a known autoimmune thyroid disease (such as Hashimoto’s thyroiditis or Graves’ disease) or has another autoimmune disorder and thyroid involvement is suspected, then one or more of the thyroid antibodies may be requested early in the pregnancy and then again near the end. These tests are used to help the doctor determine whether the baby may be at risk of thyroid dysfunction since thyroid antibodies can cross the placenta and cause hypothyroidism or hyperthyroidism in the foetus or newborn.
Thyroid antibody testing may also be requested when a patient is being investigated for infertility.
What does the test result mean?
Mild to moderately elevated levels of thyroid antibodies may be found in a variety of thyroid diseases.
Thyroid cancer is a very rare tumour, and thyroid antibodies can sometimes be detected at low level.
Significantly increased concentrations most frequently indicate thyroid autoimmune diseases such as Hashimoto’s thyroiditis, primary myxoedema, and Graves’ disease. In general, the higher the level, the more likely autoimmune thyroid disease is present. All of these antibodies, if present in the mother, can increase the risk of hypothyroidism or hyperthyroidism in the foetus or newborn.
A certain percentage of patients who are healthy may be positive for one or more thyroid antibodies. The prevalence of thyroid antibodies tends to be higher in women and tends to increase with age. If a person with no apparent thyroid dysfunction has a thyroid antibody present, the doctor will track health over time, and monitor thyroid function tests (TSH, FT4 and sometimes FT3). While most may never experience thyroid dysfunction, a few patients may develop it in the future.
Monitoring of thyroid cancer
TgAb and thyroglobulin can be used in in the monitoring of certain types of thyroid cancer. TgAb can sometimes, for technical reasons, interfere with the test results for thyroglobulin, hence why they must be requested and interpreted together. If TgAb or thyroglobulin is being used as a monitoring tool and has stayed high or dropped low initially but is increasing over time, then it may be that the treatment has not been effective and the condition is continuing or recurring. If levels are falling and/or have fallen to low or undetectable levels, then it is more likely that the therapy has been effective.
Is there anything else I should know?
There are a variety of different methods available for measuring thyroid antibodies, and different laboratories may use different methods, which may measure slightly different things. As a result of this, different laboratories may quote different reference ranges for resultsIf you are having serial testing done (for monitoring purposes), it is therefore important to have testing done by the same laboratory using the same method.
What can be done to prevent, reduce, or remove thyroid antibodies?
There are a few lifestyle changes that can prevent or eliminate thyroid antibodies. It is important for patients and their doctors to be aware of them when they are present, so that appropriate clinical decisions can be made.
Are thyroid antibodies part of routine testing?