Narrow Individual Variations in Serum T4 and T3... - Thyroid UK

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Narrow Individual Variations in Serum T4 and T3 in Normal Subjects: A Clue to the Understanding of Subclinical Thyroid Disease


This study blows the unscientific reference ranges used for diagnosis and treatment out of the water. Worth sharing with doctors who cling to outdated guidelines.

“High individuality causes laboratory reference ranges to be insensitive to changes in test results that are significant for the individual. (...)

A condition with abnormal serum TSH but with serum T4 and T3 within laboratory reference ranges is labeled subclinical thyroid disease. Our data indicate that the distinction between subclinical and overt thyroid disease (abnormal serum TSH and abnormal T4 and/or T3) is somewhat arbitrary. For the same degree of thyroid function abnormality, the diagnosis depends to a considerable extent on the position of the patient’s normal set point for T4 and T3 within the laboratory reference range.”

2 Replies

Thanks for posting and also most important.

Why don't we just go back to the original way of diagnosing : listen to patient - recognise the symptoms they describe: give a trial of NDT and increase gradually until symptom-free. No need for blood tests - save NHS lots of cash, especially when doctors have no idea how to interpret them and only take notice of the TSH which has no connection to the thyroid gland.

The study shows that people have individual set points, their fT3 and fT4 sit within narrower ranges within the population reference intervals. It's really about precision, how setting target fT3 or fT4 based on population levels won't be quite right for the individual. It doesn't explain how a patient with a normal hormone profile, even if normal for them, can be hypothyroid. There's a danger we get bogged down in fine tuning.

Ultimately Shaws comments should be the way of diagnosis and treatment but if they conflict with the numbers it is desirable to find out why so that the original cause can be identified.

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