What does free thyroxine mean?

Serum free thyroxine is a sensitive indicator of thyroid function test. Compared with serum thyroxine, it is not affected by thyroid-binding globulin, so it has higher sensitivity and can reflect thyroid function more accurately. The following diseases can cause the increase of free thyroid hormone in clinical practice, such as thyrotoxicosis, exophthalmic hyperthyroidism, painless thyroiditis with hyperthyroidism, subacute thyroiditis with hyperthyroidism, overdose of thyroid preparations, chronic thyroiditis with hyperthyroidism can cause the increase of free thyroid hormone. Hypothyroidism, pituitary or transient hypothyroidism with painless subthyroiditis, hypoalbuminemia all cause a decrease in free thyroxine.