Thyroid Function Test Total (TFT)
The thyroid gland produces the hormone thyroxine, also known as T4. This T4 is then converted into T3 (triiodothyronine) in the body. The pituitary gland produces another hormone – TSH (thyroid stimulating hormone) that controls the production of T4. If the amount of T4 is less, then the pituitary gland produces more TSH to stimulate the production of T4. If the levels of T4 go above a certain range, then the production of TSH is stopped by the pituitary gland. In this way, the pituitary gland helps in maintaining appropriate levels of the thyroid hormone in the body.
Tests that are useful in determining the thyroid function include TSH, Total T4 and Total T3.
Why is the test ordered?
The thyroid Function Test Total is used to evaluate the functioning of the thyroid gland. The test is also helpful in diagnosing hyperthyroidism and hypothyroidism, owing to several thyroid disorders and to monitor the effectiveness of treatment for these conditions.
When is the test recommended?
When a physician suspects hypothyroidism or hyperthyroidism based on the signs and symptoms of the patient, he or she may recommend the test. The test may also be suggested during the treatment of a detected thyroid condition.
How is the sample collected?
A blood sample is collected from a vein in the arm.
How to prepare for the test?
There is no special preparation required for the test. It is, however, better to conduct the test in the morning hours. It is also advisable to inform the doctor about any medication that the patient is on, as it may affect the outcome of the test.