Prevalence of unknown thyroid disorders in a Sardinian cohort

Objective: To assess thyroid function, the presence of thyroid antibodies, as well as the presence of goiter and/or nodules in subjects without a prior diagnosis of thyroid disorders, in a region with mild to moderate iodine deficiency. Design and methods: This cross-sectional study is based on data obtained from first and third visits of participants in the Sardinian survey. We performed two different analyses. In one, we assessed the prevalence of unknown thyroid dysfunctions among 6252 subjects who had a medical examination and blood collection for assays of thyrotropin, free thyroxine, and antibodies against thyroperoxidase (AbTPO) and against thyroglobulin (AbTG). In a second analysis, we evaluated the frequency of undiagnosed goiter and nodules among 3377 subjects who had a thyroid ultrasound scan. Subjects were excluded if they had a previous history of thyroid disorders or presence of goiter and/or nodules, or thyroid surgery, or if they were taking drugs that could impair thyroid function. Results: We found a low prevalence of overt thyroid dysfunction (hyperthyroidism 0.4% and hypothyroidism 0.7%). The rates of subclinical hypothyroidism and hyperthyroidism were 4.7 and 2.4% respectively. Almost 16% of participants were positive for at least one antibody and 5.2% for both AbTG and AbTPO. Nodules were detected in 17.4% of subjects and the prevalence of goiter was 22.1%. Conclusions: Undiagnosed biochemical thyroid dysfunctions, unknown nodules, and goiter were common in subjects living in a mild to moderate iodine-deficient area. In this community, thyroid disorders often go undetected and screening could be reasonable in subjects at a higher risk.