TSH fluctuations

[RoseF3]

How much does a TSH fluctuate normally? I had a blood test done and it was 3.35 and then another 6 weeks later and it was 1.9 - is this a big change or quite normal for not taking any medication?

[SeasideSusie Remembering]

RoseF3

Were both tests done under the exact same conditions. For thyroid tests we advise:

* Test no later than 9am to get highest possible TSH which is required for diagnosis.

* Nothing to eat or drink except water, this is because some foods can affect TSH and coffee affects TSH

* If you take a biotin supplement or any supplement containing biotin (eg B Complex or hair and nail supplement) then leave this off for 3-7 days (higher dose leave longest) as biotin causes false results with blood tests when biotin is used in the testing procedure (which most labs do).

So if your tests were done at different times, and if had eaten or drunk caffeine containing drinks before one and not the other, then TSH can vary quite considerably.

[RoseF3 in reply to SeasideSusie]

Ahhh that would explain it, the second result was afternoon and after eating. Thank you for clearing that up!

[shaws Administrator in reply to RoseF3]

The regime we have to follow to get the best blood results is worth it, especially if GP doesn't lower our dose.

[jimh111]

Two things can affect TSH.

1. Phase of menstrual cycle. See the bottom two graphs on this figure frontiersin.org/files/Artic... .

2. Time of day as can be seen on the top plot of this figure academic.oup.com/view-large... .

Other factors such as exposure to cold or vigourous excercise have a small effect.

[SlowDragon Administrator]

Previous post shows you have autoimmune thyroid disease confirmed by high TPO antibodies

healthunlocked.com/thyroidu...

Always test thyroid levels as early as possible in morning before eating or drinking anything other than water

Autoimmune thyroid disease frequently causes levels to fluctuate

Just testing TSH is completely inadequate

Autoimmune thyroid disease frequently causes low vitamin levels

Improving low vitamin levels is essential

[SlowDragon Administrator]

Median TSH graphhealthunlocked.com/thyroidu...

TSH has daily variation - circadian rhythm

healthunlocked.com/thyroidu...

important when you test TSH ....

researchgate.net/publicatio...

“According to the current TSH reference interval, hypothyroidism was not diagnosed in about 50% of the cases in the afternoon.”

“Further analysis demonstrated inadequate compensation of hypothyroidism, which was defined in 45.5% of the morning samples and in 9% of the afternoon samples”

ncbi.nlm.nih.gov/pubmed/252...

TSH levels showed a statistically significant decline postprandially in comparison to fasting values. This may have clinical implications in the diagnosis and management of hypothyroidism, especially SCH.

[jimh111 in reply to SlowDragon]

The authors of the study you quoted realised it was flawed. They measured post prandial TSH later in the day and as you point out TSH has a circadian rhythm. They did a follow-up study which corrected their mistake ncbi.nlm.nih.gov/labs/pmc/a... .

They asked the question "Does Time of Sampling or Food Intake Alter Thyroid Function Test?" and struggled to eat humble pie concluding "the timing of the test affects TSH" and "This indicates that the decline in TSH value is most likely due to biological factors alone" (i.e. not food).

The result is not easy to spot, it's the difference between Delta 1 and Delta 2 "Delta 1 and Delta 2 was not statistically significant (P = 0.61)". Too add to confusion I'm not sure they calculated Delta 1 and Delta 2 correctly but with my numbers it would still give the same conclusion. Time of day alters TSH, food doesn't.

The authors accept their first study was wrong. It would be better not to cite this study as it creates confusion.

[SlowDragon Administrator in reply to jimh111]

But if on levothyroxine…and delaying taking dose levothyroxine until after blood test most people would want to take levothyroxine on empty stomach

(I am aware you don’t do this….but majority do)

[jimh111 in reply to SlowDragon]

That’s fine, take the levothyroxine the night before or later on that day or after the blood test. Levothyroxine before or after the blood test makes very little difference but some also take liothyronine and this would make a big difference.

My comment was directed at the Indian study which is clearly hopeless and very misleading. It’s a shame the authors didn’t have the decency to issue a correction.

[RoseF3]

Thank you, that’s very interesting. I have a lot to learn about this autoimmune thyroid disease.