Low T3 and longevity

[Angel_of_the_North]

After seeing this in another discussion I though I'd do a little bit of web surfing.

I think we need to take into account a few things before we all decide to reduce our levo/T3/NDT.

1) Studies on calorie restriction with mice, rats, worms etc. They had no choice. Yes it might have reduced their insulin and other aging biomarkers, but how bad tempered were they? How did they feel? Apparently many showed signs of clinical depression by the end of the study. So that's a NO (unless for a short time).

2) Studies on humans. Mostly Leiden experiment and similar where families who had many members reaching their 90s were tested and found to have a genetic predisposition to low thyroid and higher TSH. The reports imply that these people all felt fine (so there's no way they'd have had a full thyroid panel if not for the study). It seems that there is a "phenotype" with "subclinical hypo". I mean really subclinical - no symptoms. I mean, if you feel fine, why would you get a test? The researchers point out that it is difficult to tell the difference between low thyroid results from diseases of aging and healthly people with low thyroid results.

Does that explain why our references ranges are high enough to make many of us feel ill? Because there a bunch of healthy people with that phenotype messing up the results for the rest of us?

fightaging.org/archives/201...

natap.org/2009/HIV/122109_0...

If I reach 90 and have a TSH of 4 and low normal T4 and T3, while feeling great, I'll thank my Dutch Jewish granny for her genes. Since I appear to have secondary hypo, I don't think It's going to happen.

[greygoose]

Great bit of research, Angel, thank you.

[Clutter]

Angel, TSH levels rise as we age, >3 is normal 75+ years.

I'm sure there are people walking around with TSH >10 who feel fine, but how fine are they really if the high TSH was an incidental find when they were having tests for something else?

Reducing T4 and T3 is likely to shorten my life by increasing the risk of cancer recurrence. If it were different, I wouldn't want to sacrifice wellbeing today for extra years/longevity.

[Angel_of_the_North in reply to Clutter]

I absolutely agree. But I think that study was trying to show that there are people who might really be fine with results (all their lives) that would have us bedridden. One of the studies also noted that variation in levels in a population was quite high, but in a person was very low - what's normal for her isn't normal for me. Shame this stuff seems to be read only by anthropologists, not endos.

Don't forget, all these elderly people and their families had thyroids and were apparently healthy. Of course, if they weren't actually healthy, it still shows that there is a link to hypo in families.

The whole point is to be well.

[Angel_of_the_North]

The Leiden study isn't all that exciting. It shows that the children and siblings of the very elderly people had lower T4 and T3 and higher TSH than their partners (non-relations!). Not by a huge amount. Anyone on thyroid meds was excluded. So they were testing people in their 50s and 60s.

biomedgerontology.oxfordjou...

[SilverAvocado]

If I recall correctly we occasionally see people on the forum who have somehow found they have a high TSH and feel pretty fine? Doctors trying to medicate and them not really understanding why.

[ValTay]

Thanks for following up and finding this research , Angel. Just a thought - it was of course FREE T4 and T3 that were low in these people. But (according to Dr Skinner) this is only a measure of presence, and doesn't show how it is being taken up by the organs. If these people could function well with these low levels, what else was going on in their bodies to enable this? Could it be that they had very good receptors and were making such good use of it that they were using it up, so that there was a lower than usual amount in the blood at any time? Or is that totally daft? I'm really just indicating how very complicated it is.

Another point - we are frequently told that TSH is only a test of pituitary function, so a high TSH may not indicate a thyroid problem. On the other hand, the pituitary seems to consider that there IS a problem if it's urging the thyroid to produce more hormone in these people. So there's the whole question of the pituitary hypothalamus thyroid axis involved, I suppose.

All very interesting ...