Evaluation of the risk of thyroid cancer following hysterectomy through meta-analysis

Objectives: Thyroid cancer is observed more frequently in women than men, possibly due to the influence of hormonal factors. This study aims to conduct a meta-analysis encompassing both prospective and retrospective observational studies to examine the risk of thyroid cancer in women who have undergone hysterectomy surgery. Material and methods: The literature search identified 356 articles by May 2022, and eight reported hazard ratios for thyroid cancer in women who underwent hysterectomy surgery. After the eliminations, we performed three different meta-analyses with studies that included patients who underwent only total abdominal hysterectomy (TAH), total abdominal hysterectomy and bilateral salpingo-oophorectomy (TAH and BSO), and underwent hysterectomy with or without BSO. The reporting of this study has been conducted in accordance with the guidelines of PRISMA (Preferred Reporting Items for Systematic Reviews and Meta-Analyses) and AMSTAR (Assessing the Methodological Quality of Systematic Reviews). Results: Our study showcases a comprehensive meta-analysis that includes eight observational studies, both retrospective and prospective, exploring the link between hysterectomy and the likelihood of developing thyroid cancer. This analysis is based on data from more than 12 million individuals, encompassing over 24,000 cases. Women who had undergone TAH (HR = 1.586, 95% CI: 1.382-1.819, p < 0.001), women who had undergone TAH and BSO (HR = 1.420, 95% CI: 1.205-1.675, p < 0.001), and women who had undergone hysterectomy with or without BSO had an increased risk (HR = 1.623, 95% CI: 1.387-1.899, p < 0.001) of developing thyroid cancer later in life. Conclusions: We found that hysterectomy had a statistically significant risk effect on the development of thyroid cancer. The limited number of previous studies, the low amount of information, the lack of homogeneous distribution of the patients in the studies, and the unknown characteristics of thyroid cancer developing after hysterectomy were the limitations of this study. Nevertheless, our findings can positively affect public health because of the potential to enlighten the etiological mechanisms leading to thyroid cancer. Future researches should first aim to explain the underlying mechanisms of developing thyroid cancer after hysterectomy.