Thyroid Function Test-2 (T3, T4, TSH)

Specimen Required

3-5cc Clotted Blood or Serum

Fasting Required

Purpose of the Thyroid Function Test-2 (T3, T4, TSH) Test

To help check how the thyroid gland is working, to diagnose thyroid disorders and to monitor the response to treatment.

When this Thyroid Function Test-2 (T3, T4, TSH) test is required

TFTs may be requested as part of a health check-up when symptoms suggest hypo- or hyperthyroidism due to a condition affecting the thyroid. They may also be requested following commencement of treatment for any detected thyroid condition.Signs and symptoms of hypothyroidism (decreased function of the thyroid) may include weight gain, dry skin, constipation, cold intolerance, puffy skin, hair loss, fatigue, and menstrual irregularity in women.Subclinical hypothyroidism is an early, mild form of hypothyroidism. It is called subclinical because only the blood level of TSH is a little bit above normal.Signs and symptoms of hyperthyroidism (increased function of the thyroid) may include increased heart rate, anxiety, weight loss, difficulty sleeping, tremors in the hands, weakness, and sometimes diarrhoea. There may be puffiness around the eyes, dryness, irritation, and, in some cases, bulging of the eyes.Subclinical hyperthyroidism is a condition in which you have low levels of TSH but normal levels of T3 and T4.

What the Thyroid Function Test-2 (T3, T4, TSH) Test Detects

The thyroid gland is situated in the neck and produces two hormones Thyroxine or T4 and Tri-iodothyronine or T3. Thyroid function tests (TFTs) are a group of tests requested to help check how the thyroid gland is working, to diagnose thyroid gland disorders and to monitor the response of thyroid disorders to treatment. TFTs include measuring the amount of the thyroid hormones, Thyroxine (T4) or Tri-iodothyronine (T3) and/or the…The thyroid gland is situated in the neck and produces two hormones Thyroxine or T4 and Tri-iodothyronine or T3. Thyroid function tests (TFTs) are a group of tests requested to help check how the thyroid gland is working, to diagnose thyroid gland disorders and to monitor the response of thyroid disorders to treatment. TFTs include measuring the amount of the thyroid hormones, Thyroxine (T4) or Tri-iodothyronine (T3) and/or the pituitary hormone, Thyroid Stimulating Hormone (TSH) in your blood. These hormones are chemical substances that travel through the bloodstream and control or regulate how fast your body uses energy. Thyroid hormones are present in the blood in either protein bound forms (the majority) or the free and active form of the hormone. Currently, the majority of UK laboratories measure the free form of the hormones – Free T4 (FT4) or Free T3 (FT3). The release of thyroid hormones into the blood stream is controlled by Thyroid Stimulating Hormone (TSH) produced by the pituitary gland, situated at the base of the brain behind the bridge of your nose. When the blood thyroid hormone concentrations are lower than normal the pituitary gland releases TSH, which in turn increases the release of T4 and T3 into the blood stream. Under normal circumstances the amount of T4 and T3 present in the blood then returns to normal and TSH production is turned off, to maintain constant blood thyroid hormone concentrations. Thyroid Function Tests usually include some combination of:TSH (thyroid stimulating hormone or thyrotropin)– to test for hypothyroidism and hyperthyroidism and to monitor thyroid replacement therapy T4 or FT4– to test for hypothyroidism and hyperthyroidism T3 or FT3– to test for hyperthyroidism See MoreSee Less

Preparation for the Thyroid Function Test-2 (T3, T4, TSH) Test

None needed; however, certain medications can interfere with the tests, so tell your doctor about any drugs that you are taking.

Sample Requirements

A blood sample taken from a vein in your arm

Additional Notes

The actual thyroid tests offered may vary between hospital laboratories. For some, a strategy is employed to perform one initial test followed by others only if needed, and in other laboratories, the initial measurement includes both FT4 and TSH, with the addition of FT3 in selected cases.

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