BackgroundBetween 10-15% of hypothyroid patients experience persistent symptoms despite achieving biochemical euthyroidism. Unexplained persistent symptoms can be a sign of somatization. This is associated with distress and high healthcare resource use and can be classified as Somatic Symptom Disorder (SSD). Prevalence rates for SSD differ depending on classification criteria and how they are ascertained, varying between 4-25%. As this has not been studied in hypothyroid patients before, the aim of this study was to document somatization in people with hypothyroidism and explore associations with other patient characteristics and outcomes. Methods Online, multi-national, cross-sectional survey of individuals with selfreported, treated hypothyroidism, that included the validated patient health questionnaire-15 (PHQ-15) for assessment of somatization. Chi-