Association Between Metabolic Dysfunction-Associated Steatotic Liver Disease and Thyroid Cancer

<b><i>Background:</i></b> Metabolic dysfunction-associated steatotic liver disease (MASLD) represents a hepatic manifestation of metabolic syndrome. This study investigated the association between newly developed nomenclature MASLD and the risk of thyroid cancer in the Korean population. <b><i>Methods:</i></b> After excluding individuals with a history of liver disease or malignancy, we analyzed a cohort of 214,502 Korean adults aged 40 years and above who participated in the National Health Screening Program from 2009 to 2010. Participants were categorized into four groups: no steatotic liver disease (SLD) without a cardiometabolic risk factor (CMRF), no SLD with at least one CMRF, MASLD, and metabolic and alcohol-related/associated liver disease (MetALD). SLD was diagnosed using a fatty liver index threshold of ≥30. The primary outcome was the diagnosis of new thyroid cancer during the follow-up period. We examined the relationship between CMRF/SLD and thyroid cancer incidence using the multivariable-adjusted Cox proportional hazards model. <b><i>Results:</i></b> A total of 2761 participants (1.3%) were newly diagnosed with thyroid cancer over an average follow-up of 9.61 years. Compared with participants without CMRF and SLD, those with CMRF (hazard ratio [HR] 1.33, confidence interval [CI] 1.16-1.52), those with MASLD (HR 1.36, CI 1.17-1.58), and the MetALD group (HR 1.40, CI 1.04-1.88) exhibited a significantly higher risk of thyroid cancer. In addition, MetALD is significantly associated with thyroid cancer incidence solely in men. <b><i>Conclusions:</i></b> In addition to CMRF, MASLD and MetALD were associated with a higher incidence of thyroid cancer in the Korean population. This study is the first to demonstrate the association between thyroid cancer and the CMRF-MASLD-MetALD continuum.