Low thyroid hormone levels linked to longer life

[JanSz]

http://www.lef.org/whatshot/index.html#lthl
October 11, 2006

Low thyroid hormone levels linked to longer life

The American Physiological Society's Comparative Physiology 2006: Integrating Diversity conference was the site of a poster session on October 9, 2006 in which Mario Pinto of City College of New York presented the finding that rodents who live longer have lower levels of the thyroid hormone T4.

Mario Pinto and Rochelle Buffenstein compared the thyroid hormone levels of mice, guinea pigs, Damara mole-rats, and naked role-rats, who can live up to 3 1/2, 6, 15 and 28 years, respectively. The blood tests were performed when the animals were at a comparable point in their life spans.

The researchers found that although T3, or triiodothyronine levels in all four species were similar, the longer-lived rodents had significantly lower levels of T4, or thyroxine, which converts to T3 in the presence of iodine. Triiodothyronine is the key hormone that regulates metabolism. Mice, whose life spans are the shortest of the four rodents compared, had T4 levels that were twice as high as those of the Damara mole-rats, and three times as high as the naked mole rats.

The study's results provide support to the theory that a more rapid metabolism is associated with a shorter life span.

"Thyroid hormones are key regulators of metabolism and have been widely implicated to influence longevity," the authors write. "Mice strains that exhibit extended longevity tend to have lower thyroid hormone concentrations than shorter living strains. Significant declines in thyroid hormone correlate well with enhanced maximum lifespan."
"These hormone concentration differences correlate with maximum species lifespan and suggest an important regulatory role of thyroid hormone in longevity," they conclude.


—D Dye