How low does TSH go from it's 9am high? - Thyroid UK

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How low does TSH go from it's 9am high?

Benos123 profile image
2 Replies

Good Afternoon,

From 2004 to 2009 my then GP prescribed Elroxin for me more based on my symptoms than my bloods and with the late Dr Peatfield's guidance from the UK, I remained symptom free up until about 2014.

However that GP retired and his replacement has repeatedly refused to prescribe Eltroxin on the basis that my TSH is "in range" and although some would say very borderline.

When I then read that if thyroid blood tests are carried out in the early morning before 9am, and that this will give the highest TSH, lowest FT4 and the most consistent results, this got me thinking that if my 0.53 TSH on the fasting blood results below was also at it's highest then that might well mean that my TSH could drift lower as the day went on and perhaps even to a point below the 0.35 "low level" entry point, and thus satisfy the GP's criteria for a prescription!

To this end, can anyone please advise how low (the range) the TSH level would most likely drift during the day?

Thanks in advance, Ben.

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RedApple profile image
RedAppleAdministrator

'can anyone please advise how low (the range) the TSH level would most likely drift during the day?'

This is probably an individual thing, like so many thyroid related things are. There's a graph somewhere that might give some pointers though. helvella might have it.

helvella profile image
helvellaAdministrator

TSH is NOT at a peak at 09:00!

It tends to fall from the early hours to some point in the afternoon.

Therefore 09:00 is on the slope down.

The links below are pretty good:

The significance of the TSH-FT3 circadian rhythm

By thyroidpatientsca on July 31, 2020

thyroidpatients.ca/2020/07/...

Circadian rhythms of TSH, Free T4 and Free T3 in thyroid health

By thyroidpatientsca on July 31, 2020

thyroidpatients.ca/2020/07/...

These are referenced in a post I made about three years ago.

healthunlocked.com/thyroidu...

Actually - just re-read your post. The doctor is more likely to prescribe when TSH is ABOVE the reference interval - not below it!

High TSH = hypothyroid

Low TSH = hyperthyroid

(Yes - that is oversimplified.)

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