Association of Metabolic Health and Central Obesity with the Risk of Thyroid Cancer: Data from the Korean Genome and Epidemiology Study.

Background: It is unknown whether the risk of thyroid cancer differs among metabolically healthy/unhealthy, normal-weight, or obese women. We aimed to assess the association of metabolic health and obesity with thyroid cancer risk.

Methods: The Korean Genome and Epidemiology Study is a population-based prospective cohort study. Data were obtained from 173,343 participants (age ≥40 years) enrolled from 2004 to 2013. Obese participants were those with body mass index (BMI) ≥25 kg/m2. Participants with abnormalities in three of these indices were considered metabolically unhealthy: triglycerides, blood pressure, high-density lipoprotein cholesterol (HDL-cholesterol), waist circumference (WC), and fasting glucose levels. Cox proportional hazards models were used to estimate hazard ratios (HR) and 95% confidence intervals (CI) for thyroid cancer risk associated with metabolic health and obesity.

Results: Compared with nonobese women without metabolic abnormalities, metabolically unhealthy women, either normal weight or obese, had an increased risk of thyroid cancer [HR (95% CI) = 1.57 (1.02-2.40) and 1.71 (1.21-2.41), respectively). Significant association was not observed in men. Thyroid cancer risk was higher among nonobese women with high WC [≥85 cm; HR (95% CI) = 1.62 (1.03-2.56)] than in nonobese women with low WC, and in obese women with low HDL-cholesterol [<50 mg/dL; HR (95% CI) = 1.75 (1.26-2.42)] compared with nonobese women with high HDL-cholesterol.

Conclusions: Metabolically unhealthy women or women with central adiposity may be at an increased thyroid cancer risk despite normal BMI.

Impact: This study suggests that women with central obesity and metabolic abnormality despite normal BMI may constitute a target group for thyroid cancer prevention and control programs.