Taken straight from the Pathology Department’s current Handbook:
"TSH only. If the TSH is outside set limits (>10 mU/L or <0.1mU/L then a free thyroxine (FT4) will be automatically undertaken. FT4 on other samples and FT3 will be added if the clinical details and TSH/FT4 results warrant it. Full clinical details are essential for this algorithm to work. If you regularly request a certain group of tests to monitor certain patients, we may be able to set up a special profile for you. Please contact Biochemistry to discuss."
It does rather sound as if the Lab makes the decision of what tests you get, which is what we always suspected, but equally it seems that a GP may be able to get round this with the will and the determination.
What I don’t understand is why they can talk about ‘the set limits’ and ‘>10mU/L’ in the same breath when the reference range for TSH at this hospital is 0.27.4.2!