Log in
Thyroid UK
93,437 members107,497 posts

Tsh and seasonal effect

1. Take a look at dates like september, august and july, for the last 3 years, how TSH number increases during summer period- this is observed in everyone, its normal body respons, that duringnsummer times when more vtiamin d is available , better metabolic rate is secured for body to replenish depleated vitamin mineral resources, for the winter, so adjusting t4 lower for the spring summer time is recommended by 10% .....in the winter lower d vitamin, tsh goes lower so body does not work on higher metabolic rate when its cold and not so much food to eat....so increasing t4 by 10% will help that natural process

2. higher TSH means better conversion from t4 to t3.....that shows on blood test, and below 1 TSH is very supressive, as seen by low ft3 numbers always acompanying it.look at readings 7and 15, on the same 150 mcg dose tsh went up for the seasonal chnage from winter to summer, and staying on the same dose made my ft3 go lower, since i was depressing it too much!instead of leavingntsh rise for summer

3. Patients who were overdosed for years, with tsh close to 0 below 0.5 it takes time months for their tsh to move away, reducing recklessly doses quickly makes these patients feel terrible, this is what i have seen in the forum very often....for overdosed patients their docs want to fix it all over night, it must go very gradually over period of 6 months or more

CONCLUSION: beeing overdosed on t4 for a long time even for years, will not proudce hyper symptoms as in the beginning( i had sweating, sleepingnproblems but i pushed and waitied and they were gradually gone!!- its seen in august 2012 my tsh dropped below 1!!) But will give you fatigue...will set you in the same position as before when you were on no meds, with few things beeingnimproved like resistance to cold, and less infections.....but giving fatigue, brain fog

Brain fog most of time is lifted by adding minimal amounts of t3 to therapy like 0.5 to 2 mcg t3

19 Replies

Ivy, it is well known that TSH fluctuates seasonally as well as according to daily circadian rhythms. I reduced my medication when the weather became hot in June. Temperature has dropped considerably in the last couple of weeks and I'm considering raising it again soon as my hands and feet are icy now.

I disagree with your statement that higher TSH enables better T4 to T3 conversion. TSH rises in response to low/falling T3 to prompt the thyroid gland to produce more T4 for conversion to T3.

Your thyroid results are individual to you and you can't extrapolate them to all hypothyroid patients. I was overreplaced on 200mcg T4 to suppress my TSH but I didn't have hyper symptoms as my FT4 and FT3 weren't elevated. 15 months later my TSH remained suppressed on 100mcg T4 but my FT4 was low and FT3 below range. I don't have hyper symptoms on 100mcg T4 + 40mcg T3 either.


If that is so then my tsh readings close to 1 and low ft3 would not happen all together:-) higher tsh does come with better conversion as is seen from the data above on many readings..the best ft3 lvls were togehter with tsh at 2.4.....also summer tsh optimum for me may be 2.4 and winter 1.4

Then why would tsh rise in the summer? If not for body to convert better t4 to t3 .....for the reason i said above:-) to me this is all logical..higher TSH number menas better conversion, and hypo people have better conversion on higher TSH, this is how body trys so hard to make steady amount of ft3 wich is cruical as we have seen for everything.....must be with very low variations

I am sure these results would be typicial for thousands of people too!and are not just my individual:-) ....this is where we will never agree so be it:-)

And you have no thyroid so you are def big outlier case for anyone who has it


Sorry they just look like random fluctuations, the readings are in random months, I would imqgine you would need a clinical trial which was controlled with a few more people in the trial. Everybodies tsh levels fluctuate so I dont think you can corrilate your readings to other people. Interesting findings for you own petsonal use though


No i dont need it, cause this was confirmed by a clinician who has 33 years of experience ,and said this is easily confirmed by data of patiens of any doctor:-) and i found them in my data too:-) and shared here ....and it explained to me my high tsh reading in summer months, and last reading tsh moved from 0.67 to 1 almost but showing how i was beeing dead now....and i felt like that! Too much of t4 150...killed it! And this is logical again 100 mcg is physiological dose and i have thyroid, am not without any

You dont have to appologise:-) , i amsory you did not find this useful:-)

All tests done at 18 h:-) ..and time of month is so absolutely irrelevant lol and is regular, no randomness at all....

I would encourage you all to do simmilar for yourself, and learn something from it...not just guess around constantly:-)


I haven't noticed mine changing with the seasons - only very slightly with time of day. Mind you, it doesn't rise when my T3 falls either.


Thats too bad, because you are probably overmedicated for many years now, nor mine tsh rise when t3 is low, its the opposite, ft3 rises with higher tsh:-) ..this is because higher tsh makes cnversion from t4 to t3faster, observed in all people, during summer months, probably having to do with vitamin d too


It's more likely that I have a pituitary problem.


Yes that can be too. But dont know your background , hystory...if you surpress tsh for just 1 year , let alone more it wont respond either correcly, but stay stuck at 0


Not suppressed, just doesn't change by more than about 0.02 ever.

How can you tell that T4 is being converted into T3 faster? Surely that would result in more T3 in the cells, therefore less TRH, less TSH, less T4 (then gradually, less T3, more TRH, More TSH, more T4 etc provided that conversion is working correctly).

Is there any evidence for the effect of TSH suppression in medicated hypo patients rather than those who are hyperthroid?


I can tell becasue i read it from experienced doctors and its seen on my data, look at my ft3 and tsh graph, when t3 is up tsh is up too, they are almost 100% in sync....

Yes there is evidence, you can see it in my data too, all 3 readings below 1 come with very low ft3

Evidence all around the place if you want to see.

Otherwise stick to mantra everyone is different lol:-) its also worthwile reading some serious literature not just forum


Lots of studies show a seasonal variation in TSH, but not the way you're suggesting. TSH is higher in the winter and lower in the summer:



This is probably due to the extra demands on your metabolism to maintain body temperature in cold weather.

I've graphed the TSH levels you provided by month - see link below. Just looks like random noise to me. You need to look at a large sample of people without thyroid problems for any kind of statistical significance, data from one person really isn't enough to draw this kind of conclusion from. Any changes you see in your own results are more likely to be due to change in medication, or progression of your thyroid failure, than true seasonal variation.



Its not random noise at all, becasue i had 2 readings of tsh in a span of 2 years at 3.98, my tsh is showing consistency, rising from january lvls to summer lvls, from whatever lvl they are , so in 3 summers,

If you have data over 10 years for yourself would be happy to analyse it for you...

So every summer my TSHwent up even though i was allready on supressive doses of t4.....this is not coincidence 3 times

Also tsh and ft3 if you graph it go exactly the same way!

Its the complete opposite from my own experience i eat the least in januray, and the most in september, metabolic rate is so much higher in summer months then winter months, it is logical too, if ancestors metabolized so much in winter probably would not have survived

And here is one study for you too , so i must be a new born lol



That's unusual, because most people I know say they eat more over winter, and tend to eat much lighter, lower calorie meals / salads etc over the summer.

It is colder in winter so your body has to work harder in order to maintain a normal temperature, i.e. your basal metabolic rate has to increase. Also plenty of evidence out there to support this, e.g.



Ofcourse because most of them hope to loose weight during summer and then get yoyo in the winter, i have no weight problems, i do lots of sports all year long...and i noticed this and reported to my doc...so it was long before i came here, so you dont think i made it up just for sake of discussion, what i am interested is the truth only, and happy to learn something...your input was valuable so thank you very much!!!!.....btw my colleague at work told me he eats more in the summer months too, he runs marathon is very healthy guy, and said he read its because summer heats make us eat more lol:-) ..like trying to cool off....seemed illogical but some have observed it too...also look at bears and other animals they dont diet in summer when there is plenty of food availible, this would be complete nonsense

Yes i know that a lot of energy we spend just keeping basal metabolism going, and this is why we becomemless active in the winter, keepingnenergy profile low, but i would not agree we spend more energy innwinter...since in summer we are all more lively, energetic..not spending on basal energy so much.....i know.....but at the sme time metabolic rate in winter may be lower, just becasue of scarcity......

Anyway...we would need just 5 more patients with a data like mine and i am sure we could conclude big things!!

I will trust my data in the mean time, they are VERYobvious....if you look better, at least for me ..and those docs blanchard patients if not for you ant the rest of the forum community:-) -this made me finally understand my summer tsh, that surprised me and i could not explain it, esp 2013 reading

I was so surprised i got it correctly with vit d connection:-) :-) now will think i am smart lol


My thyroid did not progress into failour because unlike many of you here i have full diagnosis done, ultrasound for each of the 15 readings and it shows massive improvement! You need to try harder:-)

Thanks for doing the graph but its usless like this since i was taking different doses, you should look at the chnage from winter to summer for that particular year:-) :-) ....lol........i know you cant see it very well, because 2.12 tsh in august 2012 is not so much higher then 1.3 in april:-) ..and i was even put on higher dose, while in winter higher dose would move my tsh easily:-) ...then summer 2013 my tsh 2.4 ..and i was overdosed on t4 even there:-) ...this year tsh managed to move only slightly...becasue so supressed...:-)


Wow i was soo good then i concluded tsh and vitamin d has something to do together!! Thanks for the link, my data clearly sayin something completely different, bear in mind all tests done the same time of the day, same lab!

Maybe the difference is becasue they are euthyroid and have good vitamin d lvls, and mine are borderline......but this doctor who had thousand patients observed the same pattern with his patients too, that their TSH rises in summer, and many docs giving more meds !!thats why they all end overmedicated eventually

So its all in sinc my variation is 1 and subclinicla variation was max o.7, normal population just 0.3....this may mean that this pattern only works for hypothyroid people, who most of time are vitamin d defficient, as we all know, so their TSHmoves up duringmsummer months to make up for lack of vitamin d...toincrease conversion rate of t4 to t3 ...in normal patients 0.3 seasonal variance is NOTHING, at least for you this would be noise if you cant spot on 1 variance:-)

i was borderline, but i know my vitamin d is better in september then in april......hm but probably not enough so tsh rises exactly in those vitamin d avaliable months!!

Would be so nice that here is just one more person with data set i have , here...let alone 10 how much smarter woud we be:-)


The second study confirms it better, that variations are greater in subclinical patients then eutyroid, also i think tsh rises only from may to september.....i dont know how they analized the data...becasue winter officialy starts only in december ......takingnsummer fall means taking oct and november data too.....

This is at least food for thinking....

All of my winter TSH were lower then summer....amazing


Hi ivy77 so in your opinion which is teh best dose of t4 to be on with all teh 33years of patients tsh info you have looked at as im intrigued to know. im on 125mg of levo my total t4 is 18.8 tsh 2.8 and am having my free t3 tested soon. have felt more depressed and anxious on happy pills but am waiting for endocrinologist appointment to see if i can have the addition of t3 with a lower does of t4 to help me feel better.


Ivy, it would be helpful to have references for the studies you describe - Web page URLs or journal citations.


You may also like...