TUESDAY, Nov. 30, 2004 (HealthDayNews) -- Very old people with underactive thyroid glands do not experience adverse effects and may even live longer than people of the same age with normally functioning thyroids, Dutch researchers say.
These surprising results, which appear in the Dec. 1 issue of the Journal of the American Medical Association, add fuel to an ongoing debate about whether to screen and treat the oldest for mild thyroid disease.
"Contrary to general expectation, the clinical implications of subclinical thyroid dysfunction are not as grave," said study author Dr. Jacobijn Gussekloo, an associate professor of gerontology and geriatrics at Leiden University Medical Center. "This definitely diminishes the 'need' for screening and treatment."
Subclinical hypothyroidism, meaning an underactive thyroid gland that does not result in symptoms, is extremely common, possibly affecting up to 20 percent of women over the age of 60.
"Whether this is just an abnormality that you find on blood tests that has no implication for the persons -- or whether it's something that needs to be diagnosed and treated aggressively -- is one of the most contentious issues in endocrinology because it's so common," said Dr. David S. Cooper, author of an accompanying editorial, director of the division of endocrinology at Sinai Hospital of Baltimore and a professor of medicine at Johns Hopkins University School of Medicine.
While some experts, including those at the Institute of Medicine, have advised against screening, professional groups have recommended it, Cooper added.
The dilemma plays down to the doctor-patient level. On the one hand, Cooper said, "what's the point of finding something if treating it makes you do worse?" On the other hand, he added, "as a doctor who sees patients every day, it's hard to resist treating patients like this, especially if they have more severe degrees."
Studies so far have shown conflicting evidence, but none have looked at "hard" endpoints, such as dying.
For this study, researchers followed 599 people from the time they were 85 years old until they were 89. This constituted the majority of all people living in the Dutch city of Leiden who were born between 1912 and 1914. Each participant had his or her thyroid status measured at the beginning of the study. As the study progressed, the authors looked at disability in daily life, depression, cognitive function and mortality.
Most of the study participants with abnormal thyroid function were underactive, although some had mildly overactive thyroids. None were treated.
As it turned out, the overactive cohort had a slightly worse mortality than normal people, although that had been shown before. Those with underactive hormones had even better survival, which was the new finding.
"It appeared, at least in this study, that not treating somebody was to their benefit. That's really peculiar," Cooper said.
Previous studies had found the same thing in animals.
"It's rather unexpected for us medics, but in line with experimental mice models," Gussekloo said.
No one really knows why this may be the case, but it's possible that the effects might be related to a dampened-down metabolic rate, Cooper said. Older animals also respond differently to thyroid hormone than do younger animals.
The dilemma of to treat or not to treat probably can be solved only with a randomized, double-blind clinical trial, but these are extremely expensive to undertake.
Certainly, the findings are food for thought. "Let's rethink the whole idea of screening for subclinical hypothyroidism in very old people, as this appears to have little consequence," Gussekloo said. "Let's rethink the therapeutic strategies. Should they be at lower intensity, or even withdrawn?"
"I say it's still reasonable to treat, but not be more aggressive in treatment," Cooper said. "To be not so aggressive makes sense."
More information
For more thyroid disease, visit the American Thyroid Association.
