Exploring the Potential Association between COVID-19 and Thyroid Cancer: A Mendelian Randomization Study

In order to address the ongoing debate surrounding the potential link between COVID-19 and thyroid cancer, our study was specifically designed to investigate the association between these two factors. We acquired summary data from a genome-wide association study (GWAS) concerning COVID-19 susceptibility and severity of COVID-19 in the European population, with a focus on their relationship with thyroid cancer. We applied three distinct methodologies to evaluate the causality between COVID-19 and thyroid cancer, employing Mendelian randomization (MR)-Egger, weighted median (WM), and inverse variance-weighted (IVW) approaches. Furthermore, we utilized a variety of techniques to assess pleiotropy and heterogeneity, including the MR-Egger intercept, MR-pleiotropy residual sum and outlier method (PRESSO), and Cochran's Q test. The MR analysis revealed associations between the susceptibility of COVID-19 and thyroid cancer (IVW odds ratio [OR]: 2.826, 95% confidence interval [CI]: [0.842, 9.483], P = 0.093) as well as between the risk of COVID-19 hospitalization and thyroid cancer (IVW OR: 1.630, 95% CI: [1.050, 2.529], P = 0.029). However, the relationship between COVID-19 and the occurrence of severe thyroid cancer cases was less evident (IVW OR: 1.061, 95% CI: [0.575, 1.956], P = 0.850). Our sensitivity analyses did not reveal any signs of horizontal pleiotropy or heterogeneity. Our MR study provided compelling evidence supporting a causal connection between the risk of COVID-19 hospitalization and thyroid cancer. Nevertheless, the MR results derived from genetic data do not support a causal link between susceptibility to COVID-19 and the risk of thyroid cancer or between very severe cases of COVID-19 and the risk of thyroid cancer. These findings have significant implications for further investigations into the impact of COVID-19 on health and the etiology of thyroid cancer.