FREE THYROID PROFILE (FT3, FT4, TSH)

Overview

A thyroid profile test is a group of tests that helps to evaluate the functioning of thyroid gland and to help diagnose the disorders of thyroid. These tests measure the levels of thyroid hormones such as T3, T4 and TSH in the blood.T3 & T4 are highly protein bound hormones and can be affected by numerous factors like illness, medications and genetic factors that influence protein binding. Therefore it is useful to measure the free or unbound hormone levels which correspond to the biologically available hormone pool.In primary hypothyroidism, thyrotropin (TSH,) levels will be elevated. In primary hyperthyroidism, TSH levels will be low. The ability to quantitate circulating levels of TSH is important in evaluating thyroid function. It is especially useful in the differential diagnosis of primary (thyroid) from secondary (pituitary) and tertiary (hypothalamus) hypothyroidism. In primary hypothyroidism, TSH levels are significantly elevated, while in secondary and tertiary hypothyroidism, TSH levels are low or normal. Elevated or low TSH in the context of normal free thyroxine is often referred to as subclinical hypo- or hyperthyroidism, respectively.