Does Obesity Cause Thyroid Cancer? A Mendelian Randomization Study
Open Access
- 1 July 2020
- journal article
- research article
- Published by The Endocrine Society in Journal of Clinical Endocrinology & Metabolism
- Vol. 105 (7), e2398-e2407
- https://doi.org/10.1210/clinem/dgaa250
Abstract
Background The incidence of thyroid cancer is rising, and relatively little is known about modifiable risk factors for the condition. Observational studies have suggested a link between adiposity and thyroid cancer. However, these are subject to confounding and reverse causality. Here, we used data from the UK Biobank and Mendelian randomization approaches to investigate whether adiposity causes benign nodular thyroid disease and differentiated thyroid cancer. Methods We analysed data from 379,708 unrelated participants of European ancestry in the UK Biobank and identified 1,812 participants with benign nodular thyroid disease and 425 with differentiated thyroid carcinoma. We tested observational associations with measures of adiposity and type 2 diabetes mellitus. One and two-sample Mendelian randomization approaches were used to investigate causal relationships. Results Observationally, there were positive associations between higher BMI (OR 1.15; 95% CI 1.08-1.22); higher waist-hip ratio (OR 1.16 95% CI 1.09-1.23) and benign nodular thyroid disease, but not thyroid cancer. Mendelian randomization did not support a causal link for obesity with benign nodular thyroid disease or thyroid cancer, although it did provide some evidence that individuals in the highest quartile for genetic liability of type 2 diabetes had higher odds of thyroid cancer than those in the lowest quartile (OR 1.45 CI 1.11-1.90). Conclusions Contrary to the findings of observational studies, our results do not confirm a causal role for obesity in benign nodular thyroid disease or thyroid cancer. They do however suggest a link between type 2 diabetes and thyroid cancer.Keywords
Funding Information
- British Heart Foundation and Diabetes (SBF004\1079)
- Wellcome Trust
- Royal Society (WT104150)
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