It was with some disbelief that I saw this news story yesterday. Apparently, Professor John Speakman thinks that taking thyroxine could boost our lifespan by up to 25%, because that's what it has done in mice.
Thyroxine is the hormone, produced by the thyroid, that controls your metabolic rate. The professor's tests show that the mice with the highest metabolic rates lived longest and thinks that it could mean the same for humans.
Well ,I for one can tell him what it's like to have too much thyroxine in your body and it's not very pleasant. If you go too far you end up at risk of heart failure! That's not going to prolong your life very much, is it? Obviously, he isn't going to advocate taking that enough to put you into that sort of situation, but it's hard to see how much would have a benefit before it tips the scales in favour of harming you. My thyroid is only fairly mildly hyperactive but it has had a dramatic effect on my standard of life. I wouldn't want to intentionally take something that would do that to me.