Objective: To investigate metabolic factors and their possible impact on risk of thyroid cancer.
Methods: A prospective cohort study was conducted based on seven population-based cohorts in Norway, Austria, and Sweden, in the Metabolic syndrome and Cancer project (Me-Can). Altogether 578,700 men and women with a mean age of 44.0 years at baseline were followed for on average 12.0 years. Relative risk of incident thyroid cancer was assessed by levels of BMI, blood pressure, and blood levels of glucose, cholesterol, triglycerides, and by a combined metabolic syndrome (MetS) score. Risk estimates were investigated for quintiles, and a z score distribution of exposures was analyzed using Cox proportional hazards regression.
Results: During follow-up, 255 women and 133 men were diagnosed with thyroid cancer. In women, there was an inverse association between glucose and thyroid cancer risk, with adjusted RR: 95% CI was 0.61 (0.41-0.90), p trend = 0.02 in the fifth versus the first quintile, and a positive association between BMI and thyroid cancer risk with a significant trend over quintiles. There was no association between the other metabolic factors, single or combined (Met-S), and thyroid cancer.
Conclusion: In women, BMI was positively, while blood glucose levels were inversely, associated with thyroid cancer.