What is Thyroxine (T4) test?
Insufficient production of thyroid hormones T3 &T4 is known as hypothyroidism and overproduction is termed as hyperthyroidism or thyrotoxicosis. Estimation of Serum TSH along with T3 &T4 is useful for differentiating the thyroid disorders of hypothalamic or pituitary origin from those of thyroid origin. In hypothyroidism of thyroid origin (primary hypothyroidism), the TSH level is elevated but in secondary hypothyroidism (of pituitary or hypothalamic origin) the TSH level is low.
Why get the Thyroxine (T4) test?
Estimation of T4 (thyroxine) and T3 (triiodothyronine) is used to check for thyroid diseases. Both are decreased in hypothyroidism but are increased in hyperthyroidism. When the results of T4 and T3 are borderline and conflicting free hormone levels FT3 & FT4 are estimated.
When to take this test?
AnytimeEvery 6 monthsNo particular precautions are required, unless it is recommended by your doctor.T4