How TSH and FT3 change during the year

[diogenes]

A new paper in Thyroid showing changes in TSH and FT3 over the year.

Thyroid

Vol. 28, No. 4

Thyroid Dysfunction: Hypothyroidism, Thyrotoxicosis, and Thyroid Function Tests

Seasonal Changes in Serum Thyrotropin Concentrations Observed from Big Data Obtained During Six Consecutive Years from 2010 to 2015 at a Single Hospital in Japan

Yoshihara Ai , Noh Jaeduk Yoshimura , Watanabe Natsuko , Iwaku Kenji , Kunii Yo , Ohye Hidemi , Suzuki Miho , Matsumoto Masako , Suzuki Nami , Sugino Kiminori , Thienpont Linda M. , Hishinuma Akira , and Ito Koichi

Published Online:1 Apr 2018doi.org/10.1089/thy.2017.0600

[Greybeard]

Link.

liebertpub.com/doi/full/10....

[Hidden]

diogenes. Has any research been done on T3 levels following food or exercise?. I am assuming that feeling hot after a large meal or exercise is a surge of T3 and wondering how that might affect all the bloods.

[diogenes Remembering in reply to Hidden]

Actually, with long duration exercise FT4 and FT3 levels actually fall somewhat. With meals, TSH is most affected.

[Hidden in reply to diogenes]

So TSH raises to increase available hormones to do the work of digestion I suppose and levels fall as a result of energy giving hormones being used up during exercise.

[Kitten44 in reply to diogenes]

And is TSH also affected by exercise?

If it rises, then may be a good thing when a test is due... (particularly as GP surgeries are notoriously bad at testing first thing in the morning...)

[diogenes Remembering in reply to Kitten44]

From the small studies done, it seems that TSH may rise during exercise but returns to the usual state after about half an hour after stopping.

[Kitten44 in reply to diogenes]

Thanks, still helpful to know... May resort to jumping on the spot next time they leave me hanging about for an hour, waiting to get my blood drawn!

[vocalEK in reply to Kitten44]

You should make a video of that!

[humanbean in reply to diogenes]

Actually, with long duration exercise FT4 and FT3 levels actually fall somewhat. With meals, TSH is most affected.

What do meals do to TSH? Raise it or lower it?

[diogenes Remembering in reply to humanbean]

TSH falls after eating, but FT4 not affected. Don't know about FT3 but suspect it will behave like FT4.

[humanbean in reply to diogenes]

Thanks, diogenes. So this suggests that the advice given to people on this forum to fast before testing is the correct one, if they are aiming to get the highest possible TSH. Good!

[Justiina in reply to humanbean]

I fast as I have always fasted so it gives consistent results. I try to keep the test days as similar as possible.

[humanbean in reply to Justiina]

Yes, I do too.

I am, of course, assuming that testing is being done first thing in the morning, after an overnight fast.

I once saw someone saying that they had fasted for 24 hours before a test. They had misunderstood the suggested routine!

[TSH110 in reply to diogenes]

I get boiling hot after eating (or as I eat) I read it was common in diabetics and is called gustatory sweating. I am not diabetic. It came on with Levothyroxine therapy and has not abated on NDT. So it might be due to my TSH falling? My temperature gauge is decidedly suspect with hot and cold bouts but generally I feel the right temperature not freezing cold all the time like I did on Levothyroxine and for decades before diagnosis. I have heard it is due to mitochondria then vascular tissue. Does any one really know?

[vocalEK in reply to TSH110]

Hmm. Wonder if that is at all related to Reynaud's Phenomenon which is pretty much a medical mystery.

[TSH110 in reply to vocalEK]

It looks possible according to this paper:

jamanetwork.com/journals/ja...

[lady_eve]

Thank you.