Researchers reported on Friday that low thyroid activity, one of the most treated conditions in the U.S., might actually be a sign of a long life.
The researchers said that it was too unsure at this point if people should stop taking thyroid pills, but they will be looking to see if the thyroid holds the key to a long life, at least for some people.
Dr. Martin Surks and colleagues at the Montefiore Medical Center and the Albert Einstein College of Medicine in New York studied people that lived to be 100. They found evidence that people with low thyroid were more likely in that group.
“We studied a large group of Ashkenazi Jews with exceptional longevity,” Surks told a news conference at a meeting of the Endocrine Society, specialists in human hormones.
They used a national survey of health to see what the average hormone levels are for people of various age.
The thyroid, which is found in the neck, is a gland that secretes hormones that affect metabolism. Usually, doctors check activity by looking at levels of TSH, or thyroid stimulating hormone.
High TSH levels show the thyroid is underactive, which is known as hypothyroidism. Having low levels is called hyperthyroidism, which is considered overactive.
People with lower thyroids tend to lose hair, gain weight and feel sluggish, while those with overactive ones may lose weight, feel their hearts race and have trembling hands. Both are easily treatable with a daily pill.
The researchers found 15 to 20 percent of the people over the age of 60 had TSH levels suggestive of an underactive thyroid gland. He said that he believes that may be normal for older people and may be a sign of a longer life.
“We estimate that 70 percent of old people whose TSH was minimally elevated and who were considered to have hypothyroidism were actually in their age-specific limits,” Surks said in a telephone interview.
In the study, 200 Jews were singled out that lived to be 100, and 400 of their children. Two genetic changes were linked to low thyroid function but also with extreme old age.
Animals are affected by metabolic rates; such as an elephant having a slow metabolic rate will have slow heartbeats and can live for decades. However, a mouse with a fast metabolisms only lives for just a few months.
Surks said it may be that people with low thyroid function in old age were “elephants” with a slow metabolism who can live longer, as compared to “mice” with fast metabolic rates who may have shorter natural life spans.
“If you are an older person with high TSH, this suggests you are on the road to a long life,” Surks said.
What worries him is that millions of people in the United States are being treated for hypothyroidism. “In North America, thyroid hormone is used at the drop of a hat,” he said.
His group is looking to see if that might interfere with a person’s natural life span.
He noted that having a low thyroid function before the age of 50 is a separate condition and appropriately treated with hormones.
He plans to study what the biological function of having high TSH levels might mean for cells and aging.
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