Abstract
BACKGROUND: Hashimoto's thyroiditis (HT) is the most common autoimmune thyroid disease (AITD) and is characterized by the presence of thyroid autoantibodies against thyroid peroxidase and/or thyroglobulin. Several studies have found that the global prevalence of HT has increased in recent decades, while others show the opposite. METHODS AND RESULTS: The objective of this scoping review was to synthesize and analyze the different studies that have evaluated the prevalence of HT (in adults) and the possible associated factors. The following databases were consulted, as follows: MEDLINE, Web of Science, PubMed, and Scopus. The search terms "epidemiology", "prevalence", and "Hashimoto disease" and "Hashimoto thyroiditis" were used. The search was limited to articles published between January 1965 and October 2024, and only articles in English were considered. In order to reduce selection bias, each article was scrutinized using the JBI Critical Appraisal Checklist independently by two authors. Studies were included if the number of participants (study population and/or cases and controls, depending on the study design) was clearly described and duplicate studies were excluded. A total of 59 studies were identified, the vast majority of them used a cross-sectional design, using different methods of disease assessment. CONCLUSIONS: Globally, the prevalence of HT is estimated to be between 5-10%; some areas with prevalences > 20% and others < 0.5% were identified. Prevalence is also higher in women than in men. Multiple underlying factors (genetic, epigenetic, environmental, and lifestyle), together with socioeconomic, nutritional, overdiagnosis, inter alia, may explain (at least in part) the wide variability in the prevalence of HT.