This result means that your thyroid test results are within normal limits.
Free T4 or thyroxine which is dissolved in your bloodstream is the main type of thyroxine.
However, there are other types of thyroxine and we therefore also test for thyroid stimulating hormone (TSH). This is a hormone produced by the pituitary gland in response to low thyroxine levels which stimulates the thyroid to produce more thyroxine.
Therefore if the thyroid fails, the level of TSH increases and if the thyroid produces too much thyroxine, then the TSH level is suppressed.