2
Key Points
➤ The "quality" of thyroid testing is defined by its ability to discriminate
among hyperthyroid, hypothyroid and euthyroid, including subclinical
conditions.
➤ Over the past 65 years, a progressive improvement in methods to
quantitate clinically relevant thyrotropin (TSH), thyroxine (T4), and
triiodothyronine (T3) concentrations has led to this state-of-the-art
status report on current recommendations.
➤ Because of the log-linear relationship of TSH to free T4 (fT4),
deviations of TSH concentration from population-specific reference
intervals represent the preferred initial test for evaluation of thyroid
function.
