Slightly Underactive Thyroid May Be a Plus

June 13 -- FRIDAY, June 12 (HealthDay News) -- Instead of being a medical problem in need of treatment, an underactive thyroid in old age might actually help you live longer, a new study says.

Researchers tested the levels of thyroid stimulating hormone (TSH) in 236 Ashkenazi Jews, who were about 100 years old, and their children, most of whom were in their 70s. For comparison with people not related by blood, they tested the TSH levels of the children's spouses.

The study found that the Ashkenazi centenarians had slightly elevated levels of TSH, which is a sign of mild hypothyroidism, or an underactive thyroid. The centenarian's children also had slightly elevated levels of TSH, compared with that of their spouses.

The thyroid, a butterfly-shaped gland in the front of the neck, helps regulate metabolism. Though researchers aren't sure why, a slightly slower metabolism might promote longevity.

"This is sort of a revolutionary finding," said study co-author Dr. Martin Surks, a professor of endocrinology and pathology at Albert Einstein College of Medicine and Montefiore Medical Center in New York City. "A year or two ago, higher TSH was thought to be a disease that might warrant treatment. These findings in this very select population suggest the opposite. Higher TSH could actually benefit you."

Surks and his colleagues also found that the centenarians and their offspring were more likely to have a particular variant of a TSH receptor. Those with that variant -- nearly 60 percent of the centenarians -- tended to have higher TSH levels.

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"The implication is that if you have the variant, your TSH would be a bit higher, and that may be favorable to achieving extreme longevity," Surks said. "These are not huge differences in TSH levels, but over a lifetime they could be very, very important."

The study was to be presented this week at the Endocrine Society meeting in Washington, D.C.

Hypothyroidism, or not enough thyroid hormone, can cause feelings of weakness, depression and fatigue.