USPSTF Evidence Review on Screening and Treatment of Thyroid Dysfunction

Results of an updated United States Preventive Services Task Force (USPSTF) evidence review of the literature concluded that more research is needed to determine the clinical benefits associated with thyroid screening [Ann Intern Med. 2014; DOI:10.7326/M14-1456].

These findings reiterate a similar conclusion derived from the 2004 USPSTF review that found insufficient evidence to recommend thyroid screening in asymptomatic, nonpregnant adults, as well as insufficient data to estimate the effects of early treatment on clinical outcomes in patients with subclinical hypothyroidism despite finding it a risk factor for developing thyroid disease.

The updated USPSTF guidance reviewed the benefits and harms of screening and treatment of subclinical and undiagnosed overt hypothyroidism and hyperthyroidism in adults without goiter or thyroid nodules. Unlike the 2004 review, the recent one also addressed identification and treatment of undiagnosed overt thyroid disease.

Using studies from MEDLINE and Cochrane databases from 2002 through July 2014, the review included randomized, controlled trials and observational studies of screening and treatment, particularly including thyroid screening versus no screening in adults without a history of thyroid dysfunction or obvious goiter, nodules, or symptoms (pregnant women were excluded), as well as studies of treatment versus no treatment in adults with subclinical or overt thyroid dysfunction.

The review found no studies that directly evaluated the benefits and harms of screening versus not screening on clinical outcomes.

One cohort study found a decreased risk for coronary heart disease events in patients with subclinical hypothyroidism (ie, based on thyroid-stimulating hormone levels of 4.1 mIU/L to 11 mIU/L) receiving treatment versus those receiving no treatment. However, no study found a difference in improved quality of life, cognitive function, blood pressure, or body mass index between patients who received treatment and those who did not.

Data were also scarce and of poor quality on the harms of screening, although overdiagnosis and subsequent overtreatment was suggested by 2 prospective, cohort studies that found approximately 40% of people with subclinical hypothyroidism were biochemically euthyroid after 3 years of watchful waiting.

Although a potential benefit was seen in lipid levels in patients who received treatment versus those who did not, the data were inconsistent and most studies did not show a significant difference or showed clinical significance that was uncertain. Some data showed that treatment conferred a difference of –0.7 mmol/L to 0 mmol/L (–28-0 mg/dL) for total cholesterol levels and –0.6 mmol/L to 0.1 mmol/L (–22-2 mg/dL) for low-density lipoprotein cholesterol levels.

“Despite the potential association between subclinical hypothyroidism and cardiovascular disease and congestive heart failure, there is no clear evidence that treatment improves clinical outcomes,” said the study’s lead author, J. Bruin Rugge, MD, MPH, department of family medicine, Oregon Health & Science University, Portland, in an interview with First Report Managed Care.

The USPSTF guidance concluded that more research is needed to understand the effects of treatment in patients with subclinical thyroid dysfunction, as well as in patients with screen-detected, undiagnosed overt thyroid disease.

Limitations of the study cited by the investigators included inclusion of articles only in English, small trials with short duration that used different dosage protocols, and no studies on treatment performed in the United States.—Mary Beth Nierengarten