I have many questions but I'll begin with this one. It is one question really, just put in several different ways.
How much do TSH levels vary while on levo? Are they pretty consistent so if we miss a dose for some reason or split tablets and one half is bigger than the other it doesn't affect the TSH level much?
If they are consistent is that why the medics go by TSH level rather than T$ level which will go up and down depending on how recently you took your pill?
As we're taking a bolus of T4 does the TSH show a circadian rhythm?
Just wondering.
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Yep, I was expecting to go up to 75, retest 6 weeks; but he doubled it to 100! Retest in 3 months (he prefers 3 months rather than 6 weeks), though he also said if I feel good on 100 then don't bother to retest for 6 months. I'll go via Medichecks in about 2 months I think! Then if my levels are decent and I feel fine then I'll not bother him. If not then I'll be banging on his proverbial door!
It all depends. First question: the circadian rhythm for TSH is much reduced when on T4 therapy. That said, there is a continual change from having some working thyroid, where the rhythm might still be there though subdued, or with no thyroid, where the rhythm is almost lost. Second question: do TSH changes occur when missing a dose? Probably not: but if someone has been on T4 a long time, leaving out T4 for quite some time may not raise the TSH level because its production has been inhibited for all that time. With someone new to treatment, TSH might change after a week or so. Third question: on taking T4, the worst outcome is that your FT4 might be 10% of so above the average shortly after taking a pill and stays steady afterwards. Fourth question: is measuring TSH useful in therapy? No usually. Only useful if someone has forgotten to take tablets for some time (compliance). It is no good for fine tuning use of tablets. FT3 measurement is the best way forward in this situation.
How much do TSH levels vary while on levo? Are they pretty consistent so if we miss a dose for some reason or split tablets and one half is bigger than the other it doesn't affect the TSH level much?
Things like that won't affect the TSH very much, because it reacts quite slowly. Much more slowly that the FT4.
If they are consistent is that why the medics go by TSH level rather than T$ level which will go up and down depending on how recently you took your pill?
No, that's not why medics go by TSH. They don't even know that the Free levels will go up and down depending on how recently you took your pill! They believe that it doesn't matter when you took the pill, the results will be the same (perhaps they still believe in the Tooth Fairy, too!). The problem is their lack of training in thyroid in med school. They don't know enough to work it out for themselves. They were told that the TSH is the 'gold-standard' test for diagnosing and treating, and what they learnt in med school is sacred. It all ends there. Pure ignorance, is the term I think I'm looking for.
As we're taking a bolus of T4 does the TSH show a circadian rhythm?
The TSH has a circadian rhythm whether you take T4 or not. It is highest at midnight and slowly drops throughout the day, being at its lowest in the afternoon - when most doctors like to do their testing! We always advise having a blood test before 9 am, after fasting over-night, because it's possible that the TSH also drops after eating - it certainly does after drinking coffee.
Yep, thanks, shall carry on with first thing in the morning tests, it usually means being seen faster at the blood draw as well, no one else is out of bed yet!
TSH is not consistent for many (possibly most) people whether on or off meds. That's because it is a pituitary hormone that varies according time of day (circadian rhythm), possibly according to the season of the year, as well as in response to feedback from thyroid and hypothalamus. It is "normal" for it to vary by 75% over the course of a day, so you might be normal in the morning and "hyper" in the afternoon or underactive in the morning and "normal" after lunch. It often varies less when on meds esp if you do not have a thyroid. It is measured in preference to actual thyroid hormones as it is a cheap test and very accurate - meaning that the test accurately measures TSH including low and high levels. However, it does not usefully reflect the levels of actual thyroid hormones in people with a hypothalamus or pituitary gland that is not functioning optimally - which is probably a high percentage of people with endocrine problems - esp when on thyroid meds.
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