Thyroid problems are one of the common problems faced by many young people these days. Any alteration in the hormone levels that is secreted by thyroid gland may cause a wide variety of problems in the whole body. We are going to discuss about the different tests that are available to detect thyroid problems.
There are several tests available to give a complete and accurate picture of thyroid function. The first and foremost is the history and physical signs and symptoms which provide useful information to detect the functioning of the thyroid gland. History of hair loss, fatigue, dry skin, brittle nails, numbness and tingling sensation in the fingers, hoarseness of voice, menstrual disturbances, intolerance to cold are some of the clues for a person to be suspected to have thyroid problems.
Serum T4:
This is the most common test performed to detect the function of thyroid gland. It is a blood test that is done to determine serum T4 levels by radioimmunoassay and its binding nature with the proteins. Any systemic illness, protein wasting diseases, use of androgen's and medicines like oral contraceptives, steroids, salicylates may interfere with accurate results. The normal range for serum T4 is 58.5 to 150 nmol/L.
Serum T3:
Serum T3 is 5 times as potent as T4 and has a more rapid metabolic action. This is also a blood test that measures the free and bound, or total serum content of T3. T3 level appears to be a more accurate indicator of thyroid problems. The normal range for serum T3 is 1.15 to 3.10 nmol/L.
T3 resin uptake test:
The purpose of this test is to determine the amount of thyroid hormone bound to thyroxine binding globulin (TBG) and the number of available binding sites. The normal T3 uptake value is 25% to 35%, which indicates that approximately one third of the available sites of TGB are occupied by thyroid hormone. If the number of unoccupied binding sites is low then it is hyperthyroidism, and if it is high then it is hypothyroidism. This test is more useful for those who are already on therapeutic doses of iodine.
Test of Thyroid-stimulating hormone (TSH):
The secretion of T3 and T4 by the thyroid gland is under the control of TSH which is secreted by the anterior pituitary gland. Testing TSH levels helps to differentiate disorders caused by diseases of thyroid gland itself and the disorders caused by diseases of pituitary gland.
TSH levels are tested by TSH radioimmunoassay and Thyrotropin-Releasing Hormone test.
a. TSH radioimmunoassay:
This is a simple blood test which is done to test the level of TSH in blood by radioimmunoassay. The levels are found to be increased in those with primary hypothyroidism.
b. Thyrotropin-Releasing Hormone (TRH)test:
This is a test that provides direct means of testing pituitary reserve for TSH and is useful when T3 and T4 test results are inconclusive. The test requires fasting overnight. TRH is administered intravenously half an hour before the blood samples are drawn to check TSH levels. There may be temporary facial flushing, nausea, or a desire to urinate felt when TRH is being administered.
Thyroglobulin:
Thyroglobulin is a precursor of T3 and T4 and can be reliably measured in the serum by radioimmunoassay. Thyroglobulin levels are increased in thyroid carcinoma, hyperthyroidism and sub-acute thyroiditis. They may be high in normal physiologic conditions such as pregnancy.
Radioactive Iodine Uptake Test:
Radioactive iodine uptake test measures the rate of iodine uptake by thyroid gland. Trace dose of I 131 is administered and the count by the scintillation counter, which detects the gamma rays released from the breakdown of I 131 in the thyroid. Those with hyperthyroidsm accumulate a high proportion of the I 131 and hypothyroidism exhibit a very low uptake.
Thyroid scan, radioscan, or scintiscan:
Thyroid scan is more similar to iodine uptake test, but this involves a highly focused scintillation detector which moves back and forth to study even more keenly. A printing device is attached which records a mark whenever a predetermined number of counts has been received. Scans are more helpful in determining location, size, shape and anatomic function of thyroid gland.
Other tests of thyroid function:
Some of the other tests that are useful in diagnosing and and detecting thyroid disorders include the Achilles tendon reflex time, serum cholesterol levels, electrocardiogram, muscle enzyme studies, ultrasound, computed tomography scanning, and magnetic resonance imaging. These are used to clarify and confirm results of other diagnostic studies.
There are a wide variety of tests available to detect the disorders of thyroid glands. They are mostly non-invasive (no blood and no pain). Be quick to check out whether there is any problem when you notice first symptoms which may prevent you from further complications.
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