Benefits of thyroid screening unclear, Task Force says

Researchers for the U.S. Preventive Services Task Force (USPSTF) suggested in a review that more research is needed to determine the benefits of screening asymptomatic individuals for thyroid dysfunction.

The review states that an estimated 5% of women and 3% of men in the U.S. have undiagnosed thyroid dysfunction and about 0.5% of the population may have undiagnosed overt thyroid disease, which can lead to coronary artery disease, congestive heart failure, atrial fibrillation, and decreased bone density. In 2004, the USPSTF found insufficient evidence to recommend for or against routine thyroid screening in asymptomatic adults.

In the update, researchers reviewed randomized controlled trials and observational studies of screening and treatment published through July 2014, expanding the scope of the update to include detection and treatment of screen-detected, undiagnosed overt thyroid disease. However, reviewers found no studies of treatment versus no treatment, “probably because treatment is considered the standard of care for this condition.”

The review was published online Oct. 28 in Annals of Internal Medicine.

For subclinical hypothyroidism (based on thyroid-stimulating hormone levels that ranged from 4.1 to 11.0 mIU/L), 1 fair-quality cohort study found that treatment of subclinical hypothyroidism was associated with decreased risk for coronary heart disease events versus no treatment. No study found that treatment was associated with improved quality of life, cognitive function, blood pressure, or body mass index versus no treatment. No studies were conducted in the United States.

Effects of treatment versus no treatment showed potential beneficial effects on lipid levels, but effects were inconsistent, not statistically significant in most studies, and of uncertain clinical significance. Treatment harms were poorly studied and sparsely reported. Two poor-quality studies evaluated treatment of subclinical hyperthyroidism but examined intermediate outcomes. No study evaluated treatment versus no treatment of screen-detected, undiagnosed overt thyroid dysfunction.

While screening can identify patients with subclinical thyroid dysfunction or undiagnosed overt thyroid disease, more research is needed to understand the effects of treatment, the review concluded.

“The harms of screening remain poorly studied and sparsely reported,” the authors wrote. “Potential harms of screening for subclinical hypothyroidism include false-positive test results, anxiety related to test results, and harms of treatment (including overreplacement or overtreatment), but evidence is too limited to estimate effects on any of these outcomes. Two prospective cohort studies suggest that approximately 40% of persons with subclinical hypothyroidism were biochemically euthyroid after 3 years of watchful waiting, suggesting that overdiagnosis and subsequent overtreatment could be an issue.”

A draft recommendation statement on screening for thyroid dysfunction will be posted to the USPSTF website for public comment.