Increasing Thyroxine Dose Question.

[Flatdanny]

My mother has been on thyroxine for many years and her GP has reduced her dose a number of times. Should her below range TSH be ignored if her FT3 and FT4 are not optimal? Her GP seems to be basing her decision to reduce her medication purely on TSH.

She was on 100mcg of thyroxine before and her GP made her lower her dose to 50mcg.

Thanks 🙏

[jimh111]

TSH secretion can become subnormal for various reasons. Your mom’s TSH is inconsistent with her fT3 and fT4, thus it cannot be used to judge thyroid status. Your mother will feel pretty awful with these hormone levels. Get her GP to reinstate her dose or find a doctor who will do so. If the GP is resistant she could ask for a referral to an endocrinologist on the basis of her inconsistent blood test results.

[Flatdanny in reply to jimh111]

Thanks for your reply. This is what I thought and explained to my mother. It’s very tricky dealing with GP’s who only uses TSH when deciding on a dose increase/decrease. It’s a pain.

[tattybogle]

Is this the blood test from taking 100mcg ?

[Flatdanny in reply to tattybogle]

Actually think she was on 75mcg when this test was done and then they dropped her to 50mcg.

[tattybogle in reply to Flatdanny]

on this post healthunlocked.com/thyroidu...

the first reply has links to useful discussions of the 'risks' of Low TSH vs quality of life and also a research paper to show risks to bone and heart are not a problem until TSH is below 0.04

There is also a reply from 'diogenes' further down with a good reference to a paper showing TSH is different when on Levothyroxine, and therefore not the best measure for adjusting dose.

You will need this stuff when talking to GP, who will undoubtedly say "We worry about your heart and bones when TSH is below range"

[humanbean]

You might find this link of interest :

healthunlocked.com/thyroidu...

And your mother could point out the following to her doctor :

TSH 0.226 (0.27 - 4.2) UNDER the range

Free T4 14.5 (12 - 22) 25% of the way through the range

Free T3 4.42 (3.1 - 6.8) 36% of the way through the range

In a healthy person with a healthy thyroid an under-the-range TSH would normally be associated with a Free T4 and Free T3 that were very high in range or over the range. Yet your mother's Free T4 is only quarter of the way through the range and her Free T3 is well under mid-range.

Reducing your mother's thyroxine dose will lower her Free T4 and Free T3 even more. So, as jimh111 says the TSH is inconsistent with the Free T4 and Free T3 and should not be used to determine thyroxine dose.

[Flatdanny in reply to humanbean]

Thanks for the info and link. Very interesting. So I guess I’m in the right track then re TSH not being the the best way to decide on a medication increase/decrease. We just have to convince her GP that she needs to increase her dose and then try and explain why we think only focussing one her TSH might not be the best way forward. Will see how that goes 🙂

In the mean time my mother has decided to increase her dose to 100mcg from 50mcg. She didn’t want to wait another month for her next doctors appointment. So hopefully in a month she will be feeling better and can tell the doc what she has done and hopefully they will be okay with her taking 100mcg.

Thanks again.

[humanbean in reply to Flatdanny]

Unfortunately, getting doctors to believe that TSH is not the wonderful measure that they think it is is very hard indeed.

One common reason given by doctors for objecting to low TSH is that they believe low TSH leads to osteoporosis. For ammunition against that, see the following links :

healthunlocked.com/thyroidu...

healthunlocked.com/thyroidu...

The following link is harder to use as ammunition for preventing thyroid hormones from being reduced by GPs so you'll have to read it carefully to work out what message you want to give a doctor.

thyroidpatients.ca/2020/09/...

I think my favourite bit of the link is this :

Free T3

Low Free T3 (below reference range) had the highest prevalence of AF, at 15.6%. Unfortunately, many patients in the study population were in this hormone category, since 15% of the study population had a low FT3.

Given that doctors have been taught for years to fear and/or dismiss T3 I found this particular finding to be extremely ironic.

---

If your doctor associates TSH under-range with hyperthyroidism then you could ask why your mother has such low Free T4 and Free T3.

In true hyperthyroidism Free T4 levels of around 50 or above are common, and Free T3 levels of 30 and above are also common. (Units are the same as the ones in your mother's results i.e. pmol/L.)

[Flatdanny in reply to humanbean]

Great info humanbean! Thanks for sharing. I will save all the info for my mother and her GP. Though my mother gets very overwhelmed with all of this. She actually already had osteoporosis and has done for many years.

I honestly don't understand why GP’s/endos don’t have a better understanding of these things as it’s their job. I personally find it extremely stressful dealing with doctors who don't really know what they are doing. I self medicate and manage my own HRT.

[silverfox7]

I read a comment though can’t remember where, saying that TSH is irrelevant once on medication and should only be used as a diagnostic tool.