Sorry, a bit of a Moses moment. It's the lockdown fever.
You might get somwhere with a doctor with this metaphor on subclinical hypothyroidism. Imagine a carpark for say 1000 cars. Assume the owners of the carpark have set a 2 hour time limit for staying. They don’t want to use electronic control and cameras, but want to know what is the average time spent by a car in the park. So they set on a statistician to observe cars going in and coming out (not going into the park or using numberplate recognition but just counting from the entrance/exit). After a while, with enough results the statistician calculates the average stay and the uncertainty in the result. The average stay is found to be 1 hour 10 minutes, with an uncertainty totalling 30 minutes. The owners therefore are happy that their restrictions are being obeyed so believe no further action is needed. Any one car therefore using the park in future can be assumed to obey the rules. However unknown to the statistician there were 50 cars in the park that are staying over a very long time greater than 2 hours. These are a subgroup whose behaviour is very different from the majority. But because these are a small minority their influence on the statistician’s analysis is too small to be detected. But their situation is different from the majority.
In the same way a subclinical hypothyroid group comprises a selection of those patients (the majority) who will probably get better, and a smaller subgroup who won’t. But these will be swamped out if the majority are used to decide what is going on for everyone. Only by individual examination can the minority with a poor outcome be detected and treated suitably. This argument applies to all those situations where a minority exists whose behaviour is very different from the majority – eg suitability or otherwise of T4 treatment vs T4/T3 or NDT .
Perhaps a GP might now understand the falsity of diagnosing by the numbers rather than the patient.
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diogenes
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Ha Ha It's not just the time, it's the different ranges too. I once took a van into a multistorey car park . it just fitted under the height bar at the entrance , so in i went, (carefully) unfortunately the Exit was half an inch shorter .
Awkward. Very.
I was in there a lot longer than 2 hours
Edit ...in case you're wondering ...... i eventually used my brain.... and let my tyres down a bit
1. An equal number of healthy people will have a TSH, fT3 or fT4 that falls outside the 95% reference intervals (by definition).
2. If the thyroid is damaged TSH will elevate sooner and to a greater extent than fT4 / fT4 fall.
3. There is no correlation between elevated TSH levels and severity of hypothyroidism.
If you agree with statement number 2 (and I do) then there has to be a confounding factor that produces a similar degree of hypothyroidism presenting with unchanged or reduced TSH. Otherwise we would see a correlation between TSH and symptoms, even if it wasn't a strong correlation. I suspect this is in some part due to undetected central hypothyroidism and other causes. In any event the arithmetic indicates we are only recognising about half the actual cases of hypothyroidism. I trust the mathematics more than the physicians.
Many thanks, Jim. Alas, common sense is often in short supply. You suspect that this is in some part due to undetected central hypothyroidism and other causes. As a 'suspected' case of Central Hypothyroidism or Low TSH (concurrent with low fT4 and fT3) I would argue that rather than just "undetected", it is largely ignored due to an over-reliance on measuring or monitoring TSH in blood tests as a 'signal' or 'marker' of Thyroid issues. I believe my case has been "undetected" or, I would contest, largely ignored for over 15 years now, and I've seen many many Endocrinologists in that time! I'm not sure I heard much common sense in all those years from the Endocrinology profession although, perhaps unsurprisingly, there seems to be plenty of common sense here from the "patients". However, I readily admit my patience is now wearing a little thin!
I agree it is largely ignored, because otherwise the logical conclusion is that the blood tests are not definitive and the doctors would have to admit they are wrong and revert to proper diagnosis based on signs and symptoms - this involves effort.
I don't want to divert the topic off course. My contention is mathematical. If TSH is a good marker for a failed thyroid and there is no strong correlation between TSH and symptom severity (or even existance of symptoms) then logically there has to be other factors that cause hypothyroidism independent of TSH levels.
One problem I see, and this is diogenes speciality, is that the TSH assay detects TSH molecules and isn't selective as regards detecting bioactive TSH as opposed to largely inactive TSH as in central hypothyroidism.
As the late Dr Gordon Skinner put it 'a discotheque and graveyard can have a similar degree of presence but different levels of activity'. For many of us with low normal fT3, fT4 and a normal TSH it's a bit like having a disco in a graveyard with the blood test counting all the bodies, above and below ground.
No worries! I think you're fully on topic and I really appreciate the feedback. I just wish that the 'reliance' on the TSH test could be thrown in the Burning Bush! That would be my first entry for Room 101 if I ever got invited on the show! In the mean time, I'll just enjoy the flashing lights and dance in the graveyard. My song is UB40 "I am the one in ten, even though I don't exist, a statistical reminder of a world that doesn't care!"
I've heard it said that Moses moments ( like lockdown fever!) are sourced in frustration!
As someone who needs a supraphysiological dose of T3, my treatment by medics over many years has generated a fair few of those!
To maintain the car theme, an endo who disagreed with my taking T3 tried to explain the error of my ways by suggesting that taking T3 was like setting out on car journeys ....sometimes you can arrive safely and sometimes you might crash. I kid you not!
We parted company....I took control of my T3 medication and I drove home.
Here, we all know that unlike cars, people don't roll off a production line with a user manual in the pocket. An old medic friend (a car enthusiast) once said "I'm just a mechanic for humans". He understood diagnostics (good old fashioned clinical evaluation)...he was a good doctor.
I fear my erstwhile endo would be struggling with those 1,000 cars in the car park!
I didn't know people with SCH could get better! You mean to the point of coming off meds? I thought it was just a slow dance to full hypothyroidism. What if you have antibodies?
No, remembering that a TSH result taken at a certain time is exactly that: it doesn't tell you what has been and is going to be at other times. I think that most people will have episodes of slightly elevated TSH some time in their lives (because of stress, temporary illness etc) which will go back to normality slowly or quickly. You could be unlucky and give a blood sample accidentally in one of these phases - so this means SCH is exactly that for some people - a temporary blip. That's why the presenting patient should be thoroughly examined and not pushed away "just because of the number".
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