Word of wisdom is not to check thyroid function test in ICUs as it takes only few hours for patient to ‘abnormalize’ thyroid function test under stress but if clinically indicated send full "Thyroid Function Test” including TSH, Total T3, Total T4, Free T4 and rT3 (reverse T3). There is no absolute trend but general rule of thumb is as patient get sicker and sicker “all fall but reverse rise” i.e rT3 (reverse T3) will be elevated.
