Look at this paper in PNAS. Should we give more credit to blood T3 levels now?
In my view, I simply do not see why T3 is so ignored. Therefore it is difficult to simply accept the "more credit" argument.
Longevity, demographic characteristics, and socio- economic status are linked to triiodothyronine levels in the general population
Ralph I. Lawtona, Bernardo L. Sabatinia,b,c,1, and Daniel R. Hochbauma,b,1
Contributed by Bernardo L. Sabatini; received May 23, 2023; accepted November 20, 2023; reviewed by Antonio C. Bianco and Kathleen Mullan- Harris
Significance
Thyroid hormone influences many aspects of human physiology and behavior. However, the consequences of normal variation in thyroid levels in general populations are unknown. Here, we find strong relationships between triiodothyronine (T3) levels and health and socioeconomic outcomes, notably with mortality, income, and labor participation (employment status and hours worked)
Abstract
The hypothalamic–pituitary–thyroid (HPT) axis is fundamental to human biology, exerting central control over energy expenditure and body temperature. However, the consequences of normal physiologic HPT-axis variation in populations without diagnosed thyroid disease are poorly understood. Using nationally representative data from the 2007 to 2012 National Health and Nutrition Examination Survey, we explore relationships with demographic characteristics, longevity, and socio-economic factors. We find much larger variation across age in free T3 than other HPT-axis hormones. T3 and T4 have opposite relationships to mortality: free T3 is inversely related and free T4 is positively related to the likelihood of death. Free T3 and household income are negatively related, particularly at lower incomes. Finally, free T3 among older adults is associated with labor both in terms of unemployment and hours worked. Physiologic TSH/T4 explain only 1.7% of T3 variation, and neither are appreciably correlated to socio-economic outcomes. Taken together, our data suggest an unappreciated complexity of the HPT-axis signaling cascade broadly such that TSH and T4 may not be accurate surrogates of free T3. Furthermore, we find that subclinical variation in the HPT-axis effector hormone T3 is an important and overlooked factor linking socio-economic forces, human biology, and aging.
"While increasing free T3 is protective against mortality, increasing free T4 is linked to higher levels of mortality, suggesting that the age- related decline in T3 and T3/T4 ratio have important impacts on longevity. These results parallel similar findings on free T3, T4, and deiodinase function in hospitalized and frail patients but suggest further functional importance at sub- clinical levels in the general population"
Good information - amazing that they used data from 2007-2012 - over ten years ago and there it was. Glad someone is looking at this. Once I transfer my endo to a functional doctor in April, I may print and highlight this section for my current endo. She is "so afraid" of that low TSH - I believe she said "I never test FT3 - it doesn't matter..." and she went on (and on) about how she had to be mindful of what she was prescribing - she was responsible for me and she wouldn't be able to live with herself if she let my TSH remain at 0.04.
Maybe she should consider how many older patients she is letting die by NOT testing FT3...
More likely she's worried about her career prospects if one of her patients should suffer an adverse outcome. That probably sounds a bit harsh.
I know doctors must live in constant fear of litigation and theirs is not an easy job, but personally I would appreciate it if they said they could get into trouble with the GMC, rather than dressing it up as faux concern for the patient.
But rather like politicans they've become good at spouting falsehoods. And assume we are too stupid to know when they are telling porkies 🐷
It is interesting that this was reviewed by Bianco’s who insists on “in range” TSH when treating hypothyroid patients with combination therapy.
Although this was a study of patients ostensibly without thyroid disease, extrapolation would suggest that T3 levels and not TSH are related to mortality.
I would be interested in his views…… have they changed?
I think he has changed too but dealing with the likes of certain eminent endos to get his views (and research) considered, he no doubt has a difficult passage. Wishful thinking maybe but watching him. Peter Taylor too and a guy called Salman Razvi. They all seem to be rather quietly challenging the status of thyroid ‘opinion’ as they move along. Heads and parapets come to mind.
my head is going into a spin with some of the info - it seems to be contradicting itself in some places, and also the text is contradicting some of the graphs. But I'm quite prepared to believe that I'm just terminally confused.
The negative relationship between free T3 and household resources is stronger at lower income levels (Fig. 3C).
An inverse (negative) relationship is saying that the higher the Free T3 the lower the household resources. And when income is low this inverse relationship is stronger i.e. Free T3 is even higher and household resources are even lower.
Further on it says :
Although household resources and free T3 are inversely related, Fig. 3 shows free T3, but not free T4 or TSH, is lower among unemployed men.
Presumably, unemployed men will have lower household resources than employed men.
But the above statement in italics shows that Free T3 is lower among unemployed men. Which contradicts the earlier statement in italics.
...
The appendix is worth downloading, I think. The download option is underneath the "Supporting information" after the acknowledgements.
I came across a massive study that found that those taking just Levo have a 10% lower T3 than the normal population. Given the importance of T3 to the brain and heart, I would think this would make quite a difference to the quality of life.
I have not read the whole publication, but, yes, if T3 can be linked to economy we are golden, because economy is THE driving factor for any political action taken (for better or worse)
Looking forward to really have a close look at this. Thanks helvella.
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