Log in
Thyroid UK
91,968 members106,220 posts

Advice from those diagnosed with hypothyroidism- I don't understand the Drs!?

Just a quick question for those who have been diagnosed and have their Drs "insight"

A person who has a TSH range within the NHS range of 0.27 - 4.2 is considered "normal", symptomatic or not and wont be treated. Yet many have a result over this range and they won't treat until a TSH of over 10 is achieved....so what is the point in having the range limit as 4.2? In addition to this, people who are diagnosed are given treatment aim to get a result of about 1 in the range for TSH in order to be considered as being optimally medicated. Why? Why dont they say "It's ok your result is below 10, you should feel brilliant! People who are diagnosed are told they should then be aiming for a TSH of about 1. Why if the range goes up to 4.2? (Or 10 for consideration of treatment) None of it makes sense? If TSH is so important to Drs why the disparity?

5 Replies

The range 0.27 to 4.2 is the TSH 'reference interval'. It is the statistical interval in which 95% of the healthy population falls (in precise mathematical terms it is two standard deviations). A reference interval is not a diagnostic range, but try getting an endocrinologist to understand. When the thyroid gland starts to fail TSH rises to make the thyroid work harder.

Usually, but not always, someone will not exhibit symptoms until TSH is above 10. (Endocrinologists overlook the possibility that hypothyroidism can be caused by conditions other than a failing thyroid). You can become hypothyroid with a perfectly normal TSH.

A TSH of around 1 or 2 is sometimes targeted because patients on levothyroxine treatment usually need this to get better. Levothyroxine is not as good as your own hormones, in particular it leaves out T3.


Median TSH graph showing distribution of TSH in healthy population


TSH daily variation shows time of day that test is done is an important consideration too



The 'time of the month' has a much greater effect frontiersin.org/articles/10... .

Also, the assay measures TSH presence not bioactivity. Different TSH isoforms can vary in bioactivity by up to a factor of 4x.

TSH is useful but has to be interpreted intelligently.


These are the guidelines for treatment in Leeds. Presumably each area will have similar guidelines.



Thank you for you very interesting replies and links. At first glance it didn't seems to make sense as to why there was an upper limit on the range, a diagnostic range and then a low treatment result range. Your explanations have helped.


You may also like...