Tania Smith's reply to the paper of Fitzgerald ... - Thyroid UK

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Tania Smith's reply to the paper of Fitzgerald et al I posted a few days ago.

diogenes profile image
diogenesRemembering
9 Replies

Tania has raised yet another complication in the story which she has outlined to me as here in this post:

Quote:

Thanks very much, an enjoyable read. At first it seemed that their findings were obvious ... Then I understood what the insight was. The phenomenon seems to me explainable by inverse relationship between TSH bioactivity and TSH clearance rates, and the positive relationship between TSH bioactivity and FT4 concentrations. I've been drafting a review of the science of TSH bioactivity and TSH clearance lately. TSH quality varies, not just TSH quantity. As FT4 drops, TSH bioactivity drops, and TSH that is less bioactive clears more slowly, resulting in a TSH concentration that is higher but less potent per unit.  It appears as if the pituitary is less sensitive to T4, but it may be responding to TSH potency feedback. The ultrashort feedback loop between TSH receptors and TSH secretion has power to coregulate TSH secretion.  TSH receptors in the pituitary sense a TSH of lower bioactivity and adjust secretion accordingly. Today I learned about "deconvolution" analyses that attempted to separate TSH pulsatile secretion rates from complex, individualized clearance rates. I think the analysis became a cheat, a way to pretend that TSH clearance can be predicted and ignored so that TSH variation could be attributed to the pituitary-T4 relationship alone. 

Thus, TSH quality can be a further complication. I don't know the source of these arguments so I've asked Tania to elaborate.

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diogenes
Remembering
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Hoxo profile image
Hoxo

Wow. Thyroid biochemistry is so complex. The more I read on the subject (and a lot of it is beyond my comprehension), it’s seems even more ludicrous to simplify treatment and diagnosis to TSH testing and population reference ranges.

RedApple profile image
RedAppleAdministrator in reply to Hoxo

Hoxo 'Thyroid biochemistry is so complex'

Which is probably why medics do their utmost to simplify it down to the most basic level of TSH only. Anything else is just too difficult for them to deal with 😉

helvella profile image
helvellaAdministratorThyroid UK

Thank you diogenes.

I've long appreciated that there are many forms of TSH with differing bioactivity.

But does this change in bioactivity approximate to an analog system - such that we can in practical terms think of it as continuous variable bioactivity and just consider the average/mean bioactivity.

Or do we have to consider that a mix of different bioactivity forms are more "digital" differences - such that we see differences from the precise composition of the TSH mix and not just some "average".

Diagram of TSH isoforms from this paper:

ncbi.nlm.nih.gov/pmc/articl...

Isoforms of TSH diagrams
diogenes profile image
diogenesRemembering in reply to helvella

TSH change in bioactivity is another variable confounding a simple approach to diagnosis. Variable TSH will lead after a lag, appropriate changes in thyroid response and therefor T4 supply to the body and the biochemical responses to that. Such changes may wax and wane quite quickly, so one must consider the situation as an average. If however there is a definite permanent change in either good TSH or "disabled" TSH then diagnosis is paramount.

helvella profile image
helvellaAdministratorThyroid UK in reply to diogenes

Thank you.

Tythrop profile image
Tythrop

Is this another argument against the TSH only NHS protocol for telling us we are well when i fact we are Hypothyroidally ill?

TSH110 profile image
TSH110 in reply to Tythrop

How many more do they need before they start to believe us? As if how we feel is some sort of irrelevance, when in reality it’s the nub of the matter. How did we get here? It’s insanity. I hope this does help restore some common sense in treating PEOPLE with thyroid disorder. It’s talked about as if the thyroid disorder has a life of its own, divorced from the person suffering from it.

Tythrop profile image
Tythrop in reply to TSH110

Also Im afraid a Mostly Women thing so we are week and Heartsink patients who are invisible .The only wsy is to do some kind of class action in court to cost the money..but we have no energy so cant

TSH110 profile image
TSH110 in reply to Tythrop

yes that study recently on how sexist the medical profession is when it comes to heart attacks was very shocking

amp.theguardian.com/society...

and explains a lot about the rubbish we have to put up with.

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