Medical: Diagnostics

Thyroid disorders can be diagnosed by means of the following tests and examinations.

Blood tests: Urine analysis: Diagnostic imaging:

Blood tests:

T4: thyroxine
T4 is a hormone that is produced by the thyroid gland. Some of the hormone produced is stored in the thyroid gland, and the rest is found in the bloodstream. In the blood, most of the T4 is bound to proteins (such as TBG), yet a small percentage of it flows around as 'free T4.' T4 is actually not active; it becomes active only after it is converted into T3. Purpose: to test the function of the thyroid gland.

Free T4: unbound thyroxine
Free T4 is the thyroid hormone that is found in the blood in a free form; in other words, it is not bound to a protein. Purpose: to test the function of the thyroid gland.

T3: triiodothyronine
T3 is the active form of thyroid hormone. It has an effect on many organs and processes in your body, such as the metabolism, energy consumption, growth, and brain development. Almost all of the T3 in your bloodstream is bound to proteins (such as TBG); in other words, it does not flow around in the blood in a free form. Purpose: to confirm that the thyroid gland is working too quickly or to test the function of the thyroid if FT4 and TSH analyses did not produce sufficiently clear results.

TSH: thyroid-stimulating hormone, thyrotropin
TSH is a hormone that is produced by the pituitary (a gland in the brain). TSH ensures that the thyroid gland synthesizes enough thyroid hormone (T4 and T3). If you do not have enough thyroid hormone in your body, the pituitary gland makes more TSH, so that the thyroid gland works harder and makes more thyroid hormone. If you have too much thyroid hormone in your body, the pituitary gland makes less TSH, with the result that the thyroid gland works slower and makes less thyroid hormone. Purpose: to test the function of the thyroid gland.

TRH test: thyrotropin-releasing hormone test
TRH is a hormone that is produced by the hypothalamus (a gland/organ in the brain). TRH ensures that the pituitary produces TSH. In a TRH test, TRH is injected into your blood with an IV. After three hours, a few blood samples are taken. These blood samples are analyzed to see precisely how much TSH is in your blood at that moment. This shows how well the pituitary is working. Purpose: to detect abnormalities in the control of the thyroid gland.

TBG: thyroxine-binding globulin
TBG is a protein that binds to the thyroid hormone so that the hormone is not flowing around in its free form in the bloodstream. This test is mainly done on newborns with abnormal heel prick results (with a T4 level that is too low). Purpose: to test the amount of protein present that can bind to thyroid hormone.

Tg: thyroglobulin
Tg is a protein that is produced by the thyroid gland. Purpose: to test whether functioning thyroid gland tissue is present (when congenital hypothyroidism due to the absence of a thyroid gland is suspected or as a check-up after thyroid cancer treatment).

Anti-Tg: antibodies against thyroglobulin
Anti-Tg is present in many thyroid gland disorders. There is no point in performing a Tg test if anti-Tg is present, because the amount of Tg is influenced by the anti-Tg, making the test unreliable. Purpose: to see whether a Tg-test is reliable.

Anti-TPO: antibodies against TPO
TPO (thyroid peroxidase) is an enzyme that is produced by the thyroid gland. It assists in the formation of thyroid hormone. Anti-TPO, which is made by your own immune system, targets the thyroid gland. Anti-TPO may be present if you have Hashimoto's thyroiditis (thyroid works too slowly), Graves' disease (thyroid works too quickly), or with a normally functioning thyroid gland. Purpose: to detect an auto-immune thyroid disorder.

TSI: thyroid-stimulating immunoglobulins
TSI are antibodies produced by your own immune system. They make the thyroid gland work faster. These antibodies target the TSH receptor. They make the thyroid gland produce more thyroid hormone and work more quickly. Purpose: to detect auto-immune hyperthyroidism.

TBI: thyroid-blocking immunoglobulins
TBI are antibodies produced by your own immune system. They make the thyroid gland work slower. The antibodies target the TSH receptor and make the thyroid gland produce much less thyroid hormone. Purpose: to detect auto-immune hypothyroidism.

Chromosomal and DNA analysis
Genetic testing is performed if a syndrome or another genetic abnormality is suspected. The length of time you must wait to get the result depends on the type of test. An urgent analysis of the number of chromosomes takes a few days; a standard analysis can easily take a week. Testing genes for abnormalities usually takes several weeks; it is, after all, very time-consuming and precise work.

Heel prick
When a baby is around four days old, a few drops of blood are taken using a heel prick. Tests are then done to see how much T4, TSH and TBG are in the blood. The possible results of the heel prick are normal, abnormal or borderline abnormal.

Urine analysis:

24-hour urine analysis
Your urine is collected over a full 24-hour period and stored in a special sack. The urine provides a good indication of the amount of substances that are excreted throughout that period.

Iodine excretion
This tests the amount of iodine present in the 24-hour urine sample. Your urine will contain iodine if the production of thyroid hormone is not occurring properly. Purpose: to detect the cause of congenital hypothyroidism.

Diagnostic imaging:

Ultrasound tests are performed using sound waves. A transducer (a type of microphone) sends out sound waves and then detects them again. These sound waves bounce back off the organs and structures in your body, and the ultrasound machine converts these reflected waves into images. Your thyroid gland becomes visible on the computer screen. Purpose: to determine the location and size of the thyroid gland and the presence of nodules or cysts.

Ultrasound with needle biopsy
To examine whether the cells in the nodule are benign or malignant, some tissue is taken and examined. During the needle biopsy procedure, you must remain motionless. To lessen the sensation of the needle prick, an anesthetic cream is applied. The thyroid gland is pricked with a thin needle. Using ultrasound, the needle can be guided in such a way that the tip of the needle is directed precisely into the nodule. Then, a small piece of tissue is sucked out of the nodule and is later examined in the laboratory. This examination takes approximately ten days; in other words, you do not get the results immediately. Purpose: to determine whether the cells are benign or malignant.

Radioactive iodine or technetium uptake test
For a radioactive uptake test, a small amount of radioactively labeled iodine (I-123) or technetium is administered into your bloodstream via an IV. The iodine is taken up by the thyroid gland cells, where it is stored. You can see this on the computer using a series of photos (a scintigram). These photos show to what extent the thyroid gland takes up the labeled iodine or technetium. With Graves' disease, for example, the uptake of iodine is increased in the entire thyroid gland. If you have a nodule, such as a toxic adenoma, the uptake of the iodine is increased locally. The nodule takes up a lot of iodine, but the rest of the thyroid gland does not. The amount of radioactive substance used is very minimal; it has no effect on your body. You automatically excrete the radioactive substance back out. It is therefore extra important to wash your hands thoroughly after using the toilet when you have had this test. A staff member from the Nuclear Medicine Department can provide you with more detailed information. Purpose: to make the amount of functioning thyroid gland tissue visible, whether it is too much or too little.

Radioactive iodine uptake test with perchlorate discharge test
With this scintigraphic test, perchlorate is injected via IV two hours after the injection of the iodine. After one hour, more photos are taken. These photos show whether or not the perchlorate has displaced the iodine. This only happens if the iodine cannot bind properly to the thyroid gland. If this happens, then you have an iodine organification disorder and that can cause congenital hypothyroidism, for example. Purpose: to detect disrupted uptake of iodine into the thyroid gland (iodine organification disorder).

MRI: magnetic resonance imaging
MRI involves the use of a magnetic field. Brief alterations in this magnetic field cause your body to send out radio waves which are then captured by the scanner and converted to images (photos). The bed you must lie on in the MRI scanner moves forward in very small steps, and a photo is taken at each step. Each photo shows an image of the organs and other parts of the body at that spot. These images are called slices. All the slices together provide a good image of the inside of your body; thus, the structure, form, size, and location of everything in your body becomes visible. An MRI scan makes a great deal of noise. It makes a loud, ticking sound; therefore, wearing a pair of headphones can make the experience more pleasant. This test takes a long time, between 15 and 45 minutes, depending on the area being examined. During the scan, you must lie very still. This can be quite difficult if the scan takes a while. If you are very young or have difficulty lying still, the MRI can also be performed under anesthesia.

MRI of the brain and pituitary
To get a good image of the pituitary, a contrast medium must be used. This medium, which is injected into your bloodstream via an IV, is taken up by the pituitary, making it clearly visible.

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