Seasonal Changes in Thyrotropin and Thyroid Hormones in Women of Reproductive Age

[helvella]

A topic which has been discussed numerous times.

One of the big problems is that the difference between someone who lives in a well-heated house and someone else who has little heating and spends much time outside is dramatic. This could reduce or enhance the effects reported.

Nevertheless, it highlights the utterly ridiculous approach of one test a year. If that is performed at a similar time each year, it will have the same effects of season. At the opposite time of year, test results might be significantly different. Indeed, the difference could well be enough to determine whether someone is diagnosed with a thyroid problem in the first place, and if they should have a dose adjustment.

Seasonal Changes in Thyrotropin and Thyroid Hormones in Women of Reproductive Age

1 Department of Endocrinology and Metabolism, Ankara Bilkent City Hospital, 6800 Ankara, Turkey

2 Department of Endocrinology and Metabolism, Faculty of Medicine, Ankara Yıldırım Beyazıt University, 6800 Ankara, Turkey

3 Department of Biostatistics and Medical Informatics, Faculty of Medicine, Ankara Yıldırım Beyazıt University, 6800 Ankara, Turkey

Life 2025, 15(3), 365; doi.org/10.3390/life15030365

Abstract

Background: Thyroid hormones are essential for the proper functioning of the female reproductive system. Seasonal changes in thyroid hormones in women of reproductive age are not fully understood. we aimed to investigate seasonal changes in thyrotrophin and thyroid hormones in women of reproductive age. Methods: Approximately 75,000 TSH and thyroid hormone levels measured in 32,935 women between 2019 and 2023 were evaluated on a monthly and seasonal basis. The analysis of means (ANOM) method was utilized to compare the mean transformed rank of each group or the overall mean transformed rank for TSH, FT3, and FT4 values across months and seasons. Results: The differences from the maximum to minimum median values were 13.3% for TSH, 5.2% for free T3, and 5.9% for free T4. TSH levels were significantly lower in summer and autumn and higher in winter and spring than the overall transformed mean. The rate of individuals with TSH levels below 2.5 mIU/L was higher in summer and autumn than in spring and winter. Conclusions: TSH varies seasonally in women of reproductive age. It is appropriate to consider the season as well as other parameters that affect thyroid functions while evaluating thyroid hormones.

Keywords:

thyroid hormones; reproductive age; seasonal changes; thyroid stimulating hormone

Open access:

mdpi.com/2075-1729/15/3/365

[jgelliss]

Yes I know some need an increase in T4 in the cold winter months and other are just fine with the same dose all year round. I read years ago in the book by Barbara Lougheed.Great Topics Helvella.

[healthkiwi]

Thank you. Recently a GP expressed surprise when I said I always needed to increase / decrease my NDT dose according to winter / summer. She said she'd never heard of this. I think she mentally filed it as "one of those weird things people on NDT do, not relevant to Thyroxine. Nothing for me to see here." Sigh. Always surprises and saddens me when I realise how big the learning curve is.

[thyroid-warrior in reply to healthkiwi]

It’s saddening that the medical education doesn’t seem to cultivate the logic of how that could be a scientific biological possibility even though they might not have heard of it. Body needs to do more work to keep warm in winter, more work on thyroid, so it needs more hormones…

[BadHare in reply to healthkiwi]

I take at least twice as much in winter than summer, & also adjust according to activity. I avoid talking to GPs as they don’t understand!

[thyroid-warrior in reply to BadHare]

Thanks for sharing your experience, BadHare Yours is a great example. I've read blog posts about needing more levo during winter and I heard a couple of people on the forum mentioning it. I think we probably need a consolidated post or something to highlight this scenario so more people are aware of it. Theoretically only if you are in a place where temperature don't fluctuate so much then perhaps the dosage can be more or less kept the same but nonetheless, the amount of activity could also affect the amount of levo especially for someone who likes to be active.

[BadHare in reply to thyroid-warrior]

You’re welcome!

It’s painful trying to explain anything to GPs, & the endocrinologists I’ve seen are shamefully clueless about pituitary & thyroid issues. The upside of self-medicating is doing what suits me rather than pandering to their ignorance. Took a bit of patience, as well as & trial & error. The knowledge & advice from the good folks on here has been positively life changing!

[TSH110 in reply to healthkiwi]

You’d have thought it was patently obvious to anyone. They are so far removed from the natural rhythms of nature and the lives they claim to be helping ! Small wonder they hate NDT - the very essence of the wickedness of Mother Nature herself