In recent years, the prevalence of papillary thyroid carcinoma (PTC) has been increasing in China. Literature suggests an association between non-alcoholic fatty liver disease (NAFLD) and PTC. However, there is limited research on the relationship between metabolic dysfunction-associated steatotic liver disease (MASLD)-the latest definition incorporating metabolic criteria-and the occurrence of PTC.

To explore the influencing factors of PTC onset and evaluate the predictive value of MASLD for PTC development.

A total of 642 patients who underwent thyroid nodule resection at the Third Affiliated Hospital of Soochow University from May to September 2023 were included in the study. Among them, 323 PTC patients were assigned to the malignant group, and 319 patients with benign nodules were assigned to the benign group. General characteristics were compared between the benign and malignant groups, as well as between male and female patients. Univariate and multivariate Logistic regression analyses were performed to identify factors influencing PTC. A nomogram prediction model was constructed to estimate the risk of PTC development. The predictive performance and discriminative ability of each factor and the model were assessed using ROC curve analysis.

Compared to the benign group, the malignant group had lower age, high-density lipoprotein cholesterol (HDL-C), total cholesterol (TC), and thyroglobulin antibody (TgAb), but higher proportions of males, BMI, alanine aminotransferase (ALT), triglycerides (TG), thyroid-stimulating hormone (TSH), thyroid peroxidase antibody (TPOAb), MASLD, and systemic immune-inflammation index (SII) (P<0.05). Male patients had higher BMI, ALT, TG, TPOAb, neutrophil count, lymphocyte count, monocyte count, and MASLD prevalence, but lower HDL-C, TC, TgAb, platelet count, platelet-to-lymphocyte ratio (PLR), lymphocyte-to-monocyte ratio (LMR), and SII than female patients (P<0.05). Multivariate Logistic regression analysis showed that male sex (OR=1.581, 95%CI=1.040-2.412, P=0.033), elevated BMI (OR=1.066, 95%CI=1.002-1.136, P=0.045) and elevated TSH (OR=1.662, 95%CI=1.401-1.997, P<0.001) were risk factors for PTC, while older age (OR=0.931, 95%CI=0.916-0.945, P<0.001) was a protective factor. Based on the regression equation Logit (P)=0.381+0.466×sex-0.070×age+0.503×TSH+0.086×BMI, a nomogram prediction model for PTC risk was established. The model achieved an AUC of 0.798 (95%CI=0.764-0.832) for predicting PTC, with an optimal cutoff value of 0.502, a sensitivity of 0.721, and a specificity of 0.752.

Male gender, increased BMI, and elevated TSH are independent risk factors for the development of PTC, while increasing age is a protective factor. MASLD is not an independent risk factor. The constructed combined prediction model has good clinical predictive value for the development of PTC.