TSH is a pituitary hormone that is affected by many variables, including the time of day when blood
is drawn for
the test. Doctors rely on it as
the standard for thyroid testing, but it
is actually inadequate as a diagnostic and should not be used to determine medication dosage. At best it is only an indicator, to be considered along with the more important indicators, which are symptoms, and the free T3 and free T4 levels.