Thyroid Function Test-1 (FT3, FT4, TSH)

Specimen Required

3-5cc Clotted Blood or Serum

Fasting Required

Purpose of the Test

The TFT is used to diagnose and monitor thyroid disorders, including hyperthyroidism (overactive thyroid) and hypothyroidism (underactive thyroid). Symptoms of thyroid disorders can include fatigue, weight changes, temperature sensitivity, and changes in heart rate.

When this test is required

The TFT may be requested by a healthcare provider when a person experiences symptoms of a thyroid disorder, such as fatigue, weight changes, temperature sensitivity, and changes in heart rate. The test may also be ordered as part of routine screening for people who are at increased risk of thyroid disorders, such as those with a family history of thyroid disease or autoimmune disorders.

What the Test Detects

The thyroid function test (TFT) is a blood test that measures the levels of three hormones in the bloodstream: thyroxine (T4), triiodothyronine (T3), and thyroid-stimulating hormone (TSH). T4 and T3 are hormones produced by the thyroid gland that regulate metabolism, while TSH is a hormone produced by the pituitary gland that stimulates the thyroid gland to produce T4 and T3.

Preparation for the Test

There are no specific test preparations needed for this test. However, it is recommended that the person fasting for at least 8 hours prior to the test. The healthcare provider may also recommend temporarily stopping certain medications that can affect thyroid hormone levels, such as thyroid hormone replacement therapy, for a period of time before the test.

Sample Requirements

The test requires a blood sample, typically drawn from a vein in the arm.

Additional Notes

The TFT is typically the first test ordered to evaluate thyroid function, but additional testing may be needed to confirm a diagnosis or determine the cause of abnormal results. For example, the healthcare provider may order thyroid antibody tests or imaging tests to further evaluate the thyroid gland. It is also important to note that certain medications and medical conditions can affect thyroid hormone levels, so it is important to inform the healthcare provider of any medications or medical conditions that the person has.

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