The test is for the control of the thyroid gland function.

Clinical Significance

The Thyroid Stimulating Hormone (TSH) stimulates the thyroid gland to produce and release thyroxine (T4) hormone. Greater than 99% of T4 is bound to serum proteins, but the portion that is not, free T4, is the biologically active portion. In most cases, free T4 is good indicator of thyroid function, along with TSH and other measures.