Routine health examination indicators for fatty liver disease risk stratification in adults with thyroid dysfunction: a cross-sectional study of 46,311 individuals

Background Fatty liver disease is frequently identified during routine health examinations, but practical strategies for risk stratification in adults with thyroid dysfunction remain limited. This study evaluated metabolic dysfunction-associated fatty liver disease (MAFLD) prevalence across thyroid function categories and developed health examination–based risk stratification models.Methods This retrospective cross-sectional study included 46,311 adults who underwent routine health examinations from November 2019 to February 2025. Participants were classified as euthyroid, hypothyroid, or hyperthyroid. MAFLD was defined as ultrasound-confirmed hepatic steatosis plus overweight/obesity, diabetes, or metabolic dysregulation. Logistic regression and restricted cubic spline analyses assessed thyroid-related associations. Least absolute shrinkage and selection operator regression and multivariable logistic regression were used to develop models for adults with hypothyroidism or hyperthyroidism. Discrimination, calibration, and utility for post-examination risk stratification were evaluated.Results Among 46,311 participants, 42,978 were euthyroid, 2,645 had hypothyroidism, and 688 had hyperthyroidism. MAFLD prevalence was 33.0%, 35.5%, and 19.9%, respectively. FT3 was positively associated with MAFLD, whereas FT4 was inversely associated; TSH was not independently associated after full adjustment. The hypothyroid model retained age, BMI, ALT, TG, and HDL-C, with AUCs of 0.906 and 0.901 in the training and validation sets. The hyperthyroid model retained age, BMI, FT4, ALT, and HDL-C, with AUCs of 0.918 and 0.932. Both models showed good calibration and potential utility for post-examination risk stratification.Conclusions Routine health examination indicators can stratify fatty liver risk among adults with thyroid dysfunction and may help identify individuals requiring targeted liver-metabolic follow-up. External validation and prospective evaluation are needed.