tsh or t4 to determine over medication

[Mccrae]

It’s controversial in the United States between using tsh or t4 to detect over medication. Which is the best test to conclude over medication tsh or t4? Any help would be appreciated.

[TiggerMe Ambassador]

fT3 is the active hormone so this is the best to go on... if I were only allowed one test it would be this one

[greygoose]

Totally illogical to use TSH for several reasons:

- you are assuming that the pituitary always functions 100% correctly. It doesn't.

- once the TSH gets below 1 it becomes unreliable as an indicator of thyroid status.

- once the TSH gets to zero, it can't go any lower, but thyroid hormone levels - FT4 and FT3 - can still be too low for the individual involved. This is because the pituitary is always 'served first' when it comes to thyroid hormones. This means that the pituitary can be getting all the T4/T3 it needs, but the other cells in the body are still hypo - i.e. not getting enough thyroid hormone.

- absorption of thyroid hormone by the cells in the pituitary is different to the absorption of other bodily cells.

- the pituitary only knows what is in the blood, not how much gets into the cells.

Testing FT4 - and it has to be Free T4, not total - will tell you how much of your dose you are absorbing. But, it won't tell you how much of it is being converted into T3, the active hormone needed by every single cell in your body.

Testing FT3 will tell you how much T3 you have in your blood, but it won't tell you how much is getting into the cells.

So, you need to test all three and intrepret them together, as a whole, not as three individual and separate tests, in conjunction with symptoms. For example, if the Frees are high in the blood, and the TSH is low, but you have many hypo symptoms, then it's pretty certain that thyroid hormone is not getting into the cells. Therefore, none of those results is telling you you are over-medicated. They're only telling you what's in the blood, and in the blood, thyroid hormone doesn't do anything.

It's really not as simple as most doctors believe!

[PRJ20 in reply to greygoose]

Thank you! Thank you   helvella ! Thank you     SlowDragon ! The 3 of you have just given me what I hope is the final piece in the jig-saw I need in my own thyroid journey/treatment (or lack of ☹️) of "Utter madness." (to quote helvella from not one single Dr, including 2 Endo's and, more recently, an ENT Consultant, never joining up the dots/results since 1994! 😒), with such a clear explanation of what happens in thyroid disorders. 👌

Thank you again and have a beautiful day. ☺️🌻☀️

ETA: You've also saved me (and the forum! 😂) from my writing out a post I've been struggling to find how to formulate for the best part of 2 months!! 🙃

[helvella Administrator]

After hyperthyroidism, such as Graves, with high thyroid hormone levels for an extended period of time, and consequent low/zero TSH, it can take a very long time for TSH to rise.

Indeed, some find TSH never rises significantly.

If you dosed on that basis, those who have had "definitive" treatment - maybe thyroidectomy - could end up being provided with absolutely no thyroid hormone because TSH is zero. Utter madness.

Similarly, consider someone whose TSH is zero yet FT4 and FT3 are OK. If they increase their dose, the TSH can't drop. They could take double or triple what they need and it would never be noticed in blood tests.

You simply have to look at FT4 and FT3 in anyone under treatment. I'd argue, in anyone, at any time.

When we get a Full Blood Count, there are many factors which are tested together. Simply because you cannot get a full picture from any one factor on its own. That principle is well known and enshrined in the FBC! And, for that matter, liver function tests. It just needs extending to thyroid.

[PRJ20 in reply to helvella]

When we get a Full Blood Count, there are many factors which are tested together. Simply because you cannot get a full picture from any one factor on its own. That principle is well known and enshrined in the FBC! And, for that matter, liver function tests. It just needs extending to thyroid.

👍👍👍👌👌👌 Absolutely...and the sooner the better, though I've lost hope that it will ever happen in my lifetime.

Would it surprise you to know(?) that, having recently (Dec) been given on-line access to [supposedly all] my results (190+ pages, including 'interesting' graphs!) after a back-and-forth paper trail of 6 months, my [current] GP Surgery not only: couldn't interpret the FBC's, LFT's, or any of the other tests they did over the years, with the signs and symptoms of the Hypothyroidism I've been presenting with over the years (clearly Hashi's following the initial transient Graves with TED, though they did slip the change-over from Thyrotoxicosis/Hyperthyroidism sneakily into an SCR a few years ago! 🙄); but, most blood tests - not just TFT's - were passed off as 'Normal', even when there were ones in the FBC's, LFT's, etc., marked as 'Abnormal'; and, even more mind-blowing, they actually have my weight down when classed as obese/morbidly obese as all 'Normal' with the reference ranges as [varyingly depending on dates] 0-250 Kg, 0-300 Kg and [even one] 0-400 Kg!!! 👀😵‍💫👀

As you say, "Utter madness"!

[SlowDragon Administrator]

and essential to test vitamin D, folate, B12 and ferritin levels

Low vitamin levels are extremely common when hypothyroid

We must have good vitamin levels for good conversion of Ft4 (levothyroxine) to Ft3 (active hormone)

Also very important what time of day you test

All thyroid blood tests early morning, ideally just before 9am, only drink water between waking and test and last dose levothyroxine 24 hours before test

This gives highest TSH, lowest FT4 and most consistent results. (Patient to patient tip)

[PRJ20]

Please could this be a pinned post(?), as this explains perfectly [in the replies] for everyone to understand the "Utter madness" of the current system, certainly in the UK.

[tattybogle]

re overmedication ~TSH on it's own can be misleading.

fT4 on it's own can be misleading. .. (and i daresay fT3 can be too , on occasion)

All together~ can still be misleading unless you ALSO examine the patient properly and ask carefully for any information about symptoms that could potentially be caused by overmedication.

eg . in my case when starting levo, my TSH was 2.9 / 2.5 / 2.7 on 50mcg / 100mcg / 150mcg respectively ... if you went only by TSH then any of those doses would have been deemed more or less 'adequate' for me ... the actual dose that worked best was 150mcg .. and about a year later my TSH was significantly lower on the same dose .

I have been ok for years on 150mcg with TSH 0.05 (which would be deemed to show 'overmedicated' by many GP's.. during that time my fT4 wandered around between about 50% and 120%...with no symptoms of overmedication at either end of that scale.

I did become overmedicated on that dose post menopause.... TSH and fT4 not significantly different , but with clear symptoms of overmedication (weight loss , anxiety/ overthinking/ catastrophizing , extremely 'jumpy', over frequent bowel and bladder activity, plus other stuff) .... and a slightly lower dose of 125mcg resolved the symptoms , proving the cause was indeed overmedication.

More recently , fT4 went way over range (200%/ 242%) for several months , for no apparent reason , without significantly impacting TSH, and without causing any symptoms of overmedication .. i did lower the dose a tad cos it seemed sensible, but experienced symptoms of undermedication, so on that occasion i had to put it back up .

So the answer to your question is that no single measure or observation will tell you definitively about overmedication ... you need to take 'everything' into account, including your own personal history of results. and importantly SYMPTOMS (which can in themselves also be misleading ~ not everyone experiences overmedication in exactly the same way.. it's not always the classic 'fast heart rate and sweating' ~ my overmedication was missed for several moths by 2 GP's and myself , my hear rate was not noticeably higher.)

Sometimes the indications will seem contradictory (eg TSH highish but fT4 also over range as i currently have) , then you must make a judgement based on what seems most likely. and if in doubt about conflicting results and feeling basically ok .. then wait another few mths on same dose and retest to see if there is a clear trend in a certain direction, or if it was just a blip before deciding whether to fiddle with dose or not .