Free thyroxine is also known as FT4. The test helps to measure the total level of free thyroxine present in the blood. The Free Thyroxine is among one of the major hormones that are produced by the thyroid gland. The other major hormone is called triiodothyronine (T3).
Free Thyroxine comprises of more than 805 of thyroid hormone while T3 comprises less than 10% of it. And the main function of the thyroid hormones is to the body's metabolism.
Also mostly, Free thyroxine is attached to the protein and only a fraction of 1% is not attached to the protein. The test measures that unattached F4 in the blood.
As a result of which, when the production of thyroid hormone decreases, it leads to TSh level increases. And when the T4 ad T3 level increases the TSH level decreases.
Thus this test helps to determine if the thyroid gland is functioning well. It also helps in the diagnosis of hyperthyroidism and hypothyroidism.
In some cases, the test also helps to diagnose pituitary disorders and infertility issues in a female.
There is as such no preparation required before the test. Inform your doctor of the ongoing medications.
Depending on the test results, the doctor will prescribe you further treatment and medications if required.
While high level of free thyroxine indicates hyperthyroidism which means your thyroid gland is overactive. And low level of free thyroxine indicates hypothyroidism which means your thyroid gland is underactive.
The doctor will prescribe you a change in your dietary habits and inclusion of daily activity like exercises.