Impact of thyroid cancer on the cancer risk in patients with non-alcoholic fatty liver disease or dyslipidemia

The raised prevalence of obesity has increased the incidence of obesity-related metabolic diseases such as dyslipidemia (DL) and non-alcoholic fatty liver disease (NAFLD), along with the development and progression of various types of cancer, including thyroid cancer. In this study, we investigated whether thyroid cancer in patients with DL and NAFLD could be a risk factor for other cancers. To achieve our goal, we generated two independent cohorts from our institution and from the National Health Insurance System in South Korea. Based on the ICD-10 code, we conducted exact matching (1:5 matching) and estimated the overall risk of thyroid cancer for other cancers in patients with DL or NAFLD. Univariate and multivariate analyses showed that the hazard ratio (HR) of thyroid cancer was 2.007 (95% Confidence Interval [CI], 1.597–2.522) and 2.092 (95% CI, 1.546–2.829), respectively in the institutional cohort and 1.329 (95% CI, 1.153–1.533) and 1.301 (95% CI, 1.115–1.517), respectively in the nationwide cohort. Risk analysis revealed a significant increase in the HR in lip, tongue, mouth, lung, bone, joint, soft tissue, skin, brain, male cancers and lymphoma after thyroid cancer occurred. Thyroid cancer in patients with DL or NAFLD might be a valuable factor for predicting the development of other cancers.