Study: No ill effects from mild thyroid disease

Testing is easy, but treating borderline levels might not make a difference.

By Victoria Stagg Elliott — Posted Dec. 25, 2006

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Giving weight to the argument that no action may be best for addressing subclinical thyroid dysfunction among the elderly, a study published in the Annals of Internal Medicine found no connection between this condition and mood disorders or cognitive deficiencies in those older than 65.

"There is no clinically relevant association between minor thyroid abnormality and cognition, depression or anxiety," said Lesley Roberts, PhD, lead author of the Oct. 17 piece and behavioral sciences lecturer in the Dept. of Primary Care and General Practice at the University of Birmingham, England. "In light of these findings, we do not advise screening or treating patients with subclinical dysfunction purely to prevent mental decline."

Researchers assessed the emotional state and thyroid function of 5,865 patients receiving care from primary care practices in and around Birmingham. The goal was to increase the body of evidence that could answer the longstanding question of the value of routine thyroid function testing.

It has long been known that overt thyroid problems, which produce significant symptoms, need to be diagnosed and treated, but benefits of routine screening and treatment for those with asymptomatic mild thyroid problems are unclear. The U.S. Preventive Services Task Force guidelines say insufficient evidence exists to recommend for or against routine thyroid disease screening for adults. But the American Thyroid Assn. recommends that screening begin at age 35 and be repeated every five years. "This is one of the most controversial areas in all of endocrinology, and whether primary care should be screening older people for this is all over the map," said David S. Cooper, MD, president of the group.

Whatever the official stance, such testing is becoming more common, mostly because it's easy to do. The result is an increasing number of people diagnosed with subclinical thyroid dysfunction. But it's not clear what, if anything, should be done for them.

"In my personal opinion, because of the prevalence, it's reasonable to screen," said Dr. Cooper, who also is head of the endocrinology division at Sinai Hospital and a professor of medicine at Johns Hopkins School of Medicine in Baltimore. "What we do with the information is uncertain."

Physicians who have come out against making screening routine say they need more data. It's unknown what are the long-term effects of treating patients who have the mild form of the disease, particularly since several studies have indicated that a significant percentage of those who are diagnosed are then overtreated. It's also not known what kind of threat the mild form of the disease presents to an individual's health. Several studies have suggested that it can increase the risk of heart disease, but these have not been conclusive.

"We need a formal study," said Martin I. Surks, MD, endocrinology program chair at Montefiore Medical Center and Albert Einstein College of Medicine in the Bronx, New York. "Does treatment result in any benefits that outweigh the risks?"

Dr. Surks hopes to carry out a randomized placebo-controlled trial to investigate this issue. He also led a 2002 consensus panel on the subject convened by the American Assn. of Clinical Endocrinologists, the American Thyroid Assn. and the Endocrine Society. This body concluded that evidence to support population-wide screening was lacking.

But those favoring screening say it is necessary to decide who should be monitored. Many patients' thyroids will revert to normal function, but some will progress to the more overt form of the disease. "It's worthwhile identifying it because people go on to more significant problems in the future," said George Griffing, MD, an endocrinologist and professor of medicine at Saint Louis University School of Medicine.

There is great disagreement about how many actually will progress, but until this and other questions are answered definitively, many physicians say the decision of whether to test and treat, particularly in the face of borderline numbers, is one made after discussions with the patient.

"I talk it over with the patient and say that my judgment is to do nothing. Then I test the patient again in two or three months," Dr. Surks said. "A fair number of people will resolve."

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External links

U.S. Preventive Services Task Force on screening for thyroid disease, January 2004 (link)

"Is Subclinical Thyroid Dysfunction in the Elderly Associated with Depression or Cognitive Dysfunction?," abstract, Annals of Internal Medicine, Oct. 17 (link)

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