The thyroid is an extremely important gland that is located in the neck and its main function is to produce thyroid hormones that are responsible for regulating various processes in the body such as – metabolism, energy production and control of mood. The thyroid gland produces two main hormones – triiodothyronine (T3) and thyroxin (T4). Periodic thyroid check is extremely important in case of thyroid disorders in order to keep a track of the condition and evaluate the effectiveness of the treatment.

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8 Essential Thyroid Function
Tests

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 The thyroid is an extremely important gland that is located in the neck and
its main function is to produce thyroid hormones that are responsible for
regulating various processes in the body such as – metabolism, energy
production and control of mood. The thyroid gland produces two main
hormones – triiodothyronine (T3) and thyroxin (T4). Periodic thyroid check
is extremely important in case of thyroid disorders in order to keep a track
of the condition and evaluate the effectiveness of the treatment.
 If the thyroid gland is unable to produce enough of these two hormones
due to any reason then the condition is called hypothyroidism and some of
its recognizable symptoms include weight gain, lack of energy, depression,
etc. On the other hand, if the thyroid gland produces excess of these
hormones then such a condition is known as hyperthyroidism and some of
its symptoms include sudden weight loss, palpitations, anxiety and a sense
of unrest. If a doctor suspects any of these two conditions or a thyroid
disorder, then he may order a few thyroid tests for a complete thyroid
check up – these tests are collectively known as thyroid function test and it
includes both blood tests and imaging procedures.

3. Important Thyroid Function Tests
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 Thyroid Blood Tests:
 TSH Tests:
 The most important initial thyroid blood test for understanding thyroid
function is to measure the level of TSH (Thyroid stimulating hormone) in a
blood sample. While a high TSH level means the thyroid gland is not
working effectively due to a problem directly affecting the thyroid gland
(hypothyroidism), a low TSH level indicates that a person has overactive
thyroid gland and it is producing too much thyroid hormone
(hyperthyroidism). In some cases, a low TSH level may also result due to
any abnormality in the pituitary gland. A normal TSH level means the
thyroid gland is functioning effectively.

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 T4 Tests:
 T4 is available in the blood in two forms – T4 bound to proteins and Free
T4. Protein bound T4 cannot enter the tissues that need the thyroid
hormone. Free T4 can enter the target tissues and show its effect. The
fraction of the free T4 is measured to determine how well the thyroid is
working. The thyroid blood test for measuring Free T4 is called Free T4
Index. Individuals with hyperthyroidism have elevated Free T4 Index,
whereas individuals with hypothyroidism have a low Free T4 Index. Doctors
usually recommend TSH test and Free T4 tests together to determine the
functioning of the thyroid gland with accuracy.
 T3 Tests:
 T3 test is usually done to diagnose hyperthyroidism or to measure the
severity of hyperthyroidism. Patients with hyperactive thyroid gland will
have elevated T3 level. T3 test is rarely done for hypothyroid patients. In
certain cases, such as during pregnancy or while on birth control pills, high
levels of hormones T3 and T4 can be present. This happens because
estrogen increases the level of binding proteins. In such cases, the doctor
may recommend both TSH and Free T4 test form evaluation of thyroid
function.

5. Non-Blood Thyroid Function
Tests:
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 Radioactive Iodine Uptake (RAIU) Test:
 Radioactive Iodine Uptake (RAIU) Test is by far one of the most important
thyroid tests. The thyroid gland has to pull a large quantity of iodine from
the blood in order to produce appropriate amount of T4 hormone and the
thyroid gland as a very active mechanism for performing this task.
Radioactive Iodine Uptake test measures the effectiveness of this activity.
For this test, the patient swallows a small amount of radioactive iodine.
The radioactivity of the iodine helps the doctor to track the location of the
iodine molecules in the body. This test measures the amount of radioactive
iodine that is taken up by the thyroid gland which allows the doctors to
determine whether the thyroid gland is functioning normally or not. A very
high Radioactive Iodine Uptake means overactive thyroid gland or
hyperthyroidism, while a low Radioactive Iodine Uptake means an
underactive thyroid gland or hypothyroidism.

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 Ultrasound:
 An ultrasound of the thyroid gland is an imaging thyroid check up that
reveals the size and texture of the gland as well as a pattern of
autoimmune inflammation. The images can also reveal nodules or growth
inside the gland that may indicate a malignant tumor.
 Your doctor may order a few of these tests together as a part of your
thyroid check in order to understand the functioning of your thyroid gland
and diagnose the precise cause of the thyroid disorder. The course of
treatment and medications are dependent on the results of the above-
mentioned thyroid functioning test.
 SOURCE: http://healthcheckup.com/blog/general/thyroid-function-tests/