What does t4 do during the day?

[Yeswithasmile]

Hi.

I wonder if someone could assist me in working out t4.

I’ve read that t4 is pretty stable throughout the day. So if you need your tsh to be high you need a blood test early morning.

If you need your t4 to be at it’s lowest would that be morning too? Assuming tsh raises to stimulate the t4 am I right thinking t4 would be lowest early on in the day? Hence the higher tsh?

Just wanting confirmation on a friend with a low tsh and low t4 should be taking a blood test for maximum benefit.

Hope this makes sense?!

Thank you x.

[SeasideSusie Remembering]

Yeswithasmile

The following thread shows graphs of the daily rhythms of circulating hormone. FT4 is the second graph and you can see when it's at it's lowest point:

healthunlocked.com/thyroidu...

[Yeswithasmile in reply to SeasideSusie]

Brilliant. Thanks very much indeed x.

[tattybogle]

depends if she takes Levo or not ?In untreated people fT4 follows a little behind TSH, so it's highest overnight/early AM like TSH.

In people taking levo it's highest about 4 ish hours after taking last dose.

[tattybogle in reply to tattybogle]

thyroidpatients.ca/2020/07/...

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[Yeswithasmile in reply to tattybogle]

You posted this as I hit ‘reply’. Thanks so much!!

[Yeswithasmile in reply to tattybogle]

Thanks for the reply.

No she doesn’t take any meds. According to Medichecks her tsh is low and her t4 just below range. Doctor has booked a call for next week 🙄 and bloods via gp booked for a few weeks time 🙄 again. I just wanted to help her get them to take her seriously this time.

Thanks for your help 😊

[Jazzw in reply to Yeswithasmile]

If both are low (TSH and FT4) her doctor ought to be querying secondary hypothyroidism (aka central hypothyroidism)—which strictly isn’t a thyroid issue at all. It can be a pituitary or hypothalamus issue.

Alas, many doctors don’t seem to think about secondary hypothyroidism.

[Yeswithasmile in reply to Jazzw]

Yes. Thank you. I did post at the end of last week asking about it being a pituitary problem as that is what my uneducated opinion thought. I told her it was beyond my pay scale 🤣 but would try to do my best to help. I figured that her tsh is irrelevant now as it’s low so if we could time her blood tests so her t4 (just below range) to be as low as poss they will actually do something about it now if you catch my drift. I doubt they have ever tested her properly. Same old same old 🙄.

Thanks Jazzw. x.

[Jazzw in reply to Yeswithasmile]

Bit more about it here:

nhslcg.scot.nhs.uk/wp-conte...