TSH and menstrual cycle

[GussyG]

Morning knowledgable folks, I’m wondering about the interplay between TSH levels and the menstrual cycle. Is there any data and/or practice around testing TSH at certain time points in your cycle? I know thyroid hormone and oestrogen are linked, which also makes me wonder about the dramatic fluctuations in perimenopause and therefore the most reliable testing time. Should testing be done at the same point in your menstrual cycle? Presumably you want to keep as many variables controlled as possible. Btw I’m aware treatment shouldn’t be based on TSH levels (unlike the majority of doctors). Thoughts welcome!

[TiggerMe Ambassador]

If you can as you say reduce the variables then it's going to give you a clearer view at a specific time of the month but often the logistics of pulling this off make it tricky 😬

I do tend to put notes next to results that didn't follow the usual conditions... like the ones that get sprung on you

[GussyG in reply to TiggerMe]

Yes definitely easier to schedule if you’re doing your own blood tests otherwise you’re at the mercy of the NHS and we all know how that goes! I think for most women who track their cycle and treat themselves it’s pretty simple to schedule, depending on availability of blood test appointments. Where I live I’m fortunate I can get a test within a few days of calling up at the time I want (ie before 9am). Of course I have to pay and it’s not cheap!

I don’t know how much the fluctuation in TSH is across a typical cycle and it’s likely to have individual variation, but given treatment is either started, denied or changed based on a single measurement in time it seems prudent to measure at the same point in your cycle? Unless of course the fluctuation in TSH is very minor and deemed insignificant. I’d be interested to read any studies that show a significant relationship.

[TiggerMe Ambassador in reply to GussyG]

thyforlife.com/you-thyroid-...

This suggests mid cycle when oestrogen levels peak and can cause TSH to rise, which makes sense as when adding HRT often a little increase in thyroid hormone is needed

[tattybogle in reply to GussyG]

"I’d be interested to read any studies.... "

well gussy ...... you probably won't be too surprised to learn ~ for a common condition affecting mainly females , many of whom are diagnosed with it long before they reach menopause ..... no one has seen fit to do any research at all on how menstrual cycle affects TSH levels .

jimh111 used to have a reference paper with some observations about time of cycle / TSH levels , (which were noticed by complete fluke , they weren't deliberately researching menstrual cycle effects on TSH, heaven forbid !) in ... wait for it .... 2 ladies ~yes a whole 2 of them ~ i can't remember where it was now , but he might be able to find it (when he comes back from gallivanting)

[GussyG in reply to tattybogle]

Well now who’d have guessed that something affecting 1 in 8 women (women being half of the population) hasn’t been looked at. Unbelievable and unsurprising.

I’ve just had a quick look and found this paper:

pubmed.ncbi.nlm.nih.gov/297...

“When the women were at the beginning of their cycles, their TSH levels averaged at 1.78. At the peak of estrogen (similar to what would occur just prior to ovulation), TSH increased four-fold to 3.30. Additionally, 31 percent of women had a TSH above 4.0 during peak estrogen timing.”

A four-fold increase in TSH mid cycle is significant I’d say! Although this is only in 55 women. Clearly more research is needed. The study concludes:

“Reference bands of serum TSH dependent on the phases of the menstrual cycle should be available.”

Personally I’m going to try and keep my testing in the same phase, ie when it’s lowest (luteal).

It does raise the question about HRT and raising oestrogen levels could lead to increased TSH. Mine increased over several years since I started HRT, although is now coming down on levo.

[tattybogle in reply to GussyG]

yes , that is in line with the sort of difference found in TSH from the 2 cases i vaguely remember ..... a very significant difference in TSH , which shamefully , the TSH obsessed endocrinology profession apparently isn't aware of, or interested in .

[jimh111 in reply to tattybogle]

doi.org/10.3389/fendo.2017....