TSH + Free T4 thyroid
TSH + Free T4
TSH (= Thyroid Stimulating Hormone) is made in the pituitary gland (brain appendage) to stimulate the thyroid gland to produce thyroid hormone. Too high a TSH fits a poorly functioning thyroid, a low TSH fits an overly functioning thyroid.
A very small percentage of T4 is present in the blood as free hormone (about 0.03% is unbound). Only the free T4 (FT4) is able to exert hormonal action.