I came across this the other day. Is it as dodgy as it looks? Does it have any utility?
Jostel's TSH index
Reference range 1.3–4.1
Jostel's TSH index (TSHI or JTI), also referred to as Jostel's thyrotropin index or Thyroid Function index (TFI) is a method for estimating the thyrotropic (i.e. thyroid stimulating) function of the anterior pituitary lobe in a quantitative way. The equation has been derived from the logarithmic standard model of thyroid homeostasis. As of 2014 further study is required to show if it is useful.
This is one of the useful empirical estimations of TSH. Together with these, it makes a good estimate of actual maximum possible TSH output by the pituitary.
I'm confused as to how to calculate Jostel's index (I'm looking at my son's past results as there's question mark over whether he has central hypothyroidism. He has growth hormone deficiency). Can anyone advise how to do this? Endo is suggesting TRH test but second opinion says no, it's not necessary. I saw Hostel's Index mentioned as something that can be helpful to understand. Thanks
Download the spreadsheet and open it (it was created in Excel but is likely to work fine in other spreadsheet software such as Libre Office or Google documents or online Microsoft Office).
Just type in the TSH and FT4 numbers (which are green) and you should see the Jostel index appear (blue).
I have literally created this in response to your request so it is untested! Please don't rely on it alone.
Looking at that spreadsheet and if it is correct, none of my son's test results (he's had 15 in total in the last few years) have been outside the reference range stated in wikipedia (1.3-4.1). His lowest was 1.69 but the rest were 2-3.5. I can't access the full article to understand what these results might mean and if that reference range is correct.
I read guidelines* suggesting that where central hypothyroidism is suspected but not clear, certain other measures can be used to confirm it and that includes TRH test but also TSHI log. I didn't want to subject my son to the TRH test as second endo recommended against it and if there are other non-invasive measures, that would be preferable. We know he is at risk of central hypothyroidism because he has growth hormone deficiency. If anyone has any more info on TSHI, that would be great, TIA.
This was enormously helpful- I was very ashamed to admit how really ignorant I am at maths when I tried to do mine. It wasn’t even that nobody tried to teach me, just that I tried even harder not to listen. In the end, I asked a friend to do it for me, and he produced, using my personal values (tsh 0.1 and ft4 10.0) the same number your spreadsheet did, minus 0.957585, spreadsheet minus 0.96
I was impressed, not only by the fact that the number was replicable, but also by the fact that my THSI is so far below the lower limit of Jostel’s parameters, (1.3).
Demonstrating that you have secondary hypothyroidism is hellishly difficult, at least in my experience, and this is the most likely looking piece of evidence I’ve been able to come up with so far. I am just starting with a new endocrinologist, and I’m very glad to have something to show him. I’m still very embarrassed that I can’t do the calculation myself, even with a calculator with a log natural function- he might ask me to show me my workings like a maths teacher, and he certainly will be unimpressed with the quality of my argument.
In the Wikipedia version of the formula, it says use log natural, but in the rubric below, the article by Jostel says log. So does the European Thyroid Association article about the diagnosis and management of CH, where I first found it. Surely these are two different formulas? Is it just lazy editing or does it make a difference?
Can you help me so that I can refer to my piece of evidence without showing myself up for the lazy ignoramus I am (and many many thanks for the validation). If I lose my levothyroxine prescription again I think I will genuinely lose the will to live.
Can you think of a reasonably elegant way to express in words the thing that Jostel’s illustrates- the fact that a tsh /t4 relationship can just look wrong?
My initial diagnosis was subclinical hyperthyroidism. When I joined TUK, and came here with my results, people pointed this out at once. My tsh was 0.1, but my ft4 was at the bottom of the range, and although low tsh with t3/t4 in range are said to indicate hyperthyroidism, the ratio just looks wrong. I knew as soon as I tried t3 that my problem was too little thyroid hormone, not too much, and further study by me showed that my tsh wasn’t suppressed by high levels of thyroid hormones- that was all the tsh my damaged pituitary could make (Sheehan’s Syndrome). I now seem to be trapped in an endless revolving door where an expensive private endo prescribes Levo, and then when my gp sees my suppressed tsh, it gets stopped again. I am a bit fed up that they won’t read up on secondary hypothyroidism, yet are quite happy to make me horribly ill.
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