BACKGROUND/PURPOSE: Hypothyroidism often goes undiagnosed, yet many organizations do not recommend population screening for thyroid disease, citing low prevalence. We hypothesized that thyroid testing can be appropriate in some settings. We collected thyroid function tests and patient-reported symptoms and demographics at a thyroid screening health fair to identify characteristics associated with a greater likelihood of thyroid disease.

METHODS: We prospectively studied patients who responded to advertisements for a thyroid screening health fair in Michigan. Health fair participants were tested with a third-generation supersensitive thyroid stimulating hormone (TSH) assay, and completed the Thyroid Symptoms Questionnaire.

RESULTS: 794 of 858 people who presented to the health fair enrolled in the study. 148 people had abnormal thyroid function, 97 of whom were previously undiagnosed (12.2% of the population tested). The remaining 51 with abnormal thyroid function were taking thyroid medication; nearly half on thyroid medication were not in the therapeutic range of TSH.

No individual symptom or combination of symptoms discriminated between hypothyroid and euthyroid individuals; hypothyroid and euthyroid participants reported each symptom with a similar prevalence. However, when the prevalence that each symptom was reported in this health fair population was compared with a previously published case-control study* using the same questionnaire, we found that health fair participants reported each thyroid symptom at a higher prevalence than did the euthyroid controls in the case-control study.

CONCLUSIONS: Although specific symptoms did not discriminate between abnormal and euthyroid states, symptoms were reported at a higher rate in this self-selected health fair population than in prior studies of the general population*. Consistent with health fair attendees in general, enrollees likely participated in the thyroid health fair because of perceived symptoms and/or concern for thyroid disease. Testing such an enriched population of individuals who report more symptoms may increase yield, in this case from <2% in the general population to 12% - a finding we call the “health fair effect”. Thus, thyroid testing of people who think they have thyroid disease can be productive. Screening such populations that report more traditional thyroid symptoms may be both effective and appropriate. *Canaris GJ, Steiner JF, Ridgway EC. Do traditional symptoms of hypothyroidism correlate with biochemical disease? J Gen Intern Med. 1997;12:544-550.