Purpose: No conclusive information is available about the association between hypothyroidism or hyperthyroidism and risk of colorectal cancer (CRC). We therefore aimed to summarize the findings of observational studies on the relation between hypothyroidism or hyperthyroidism and risk of CRC.
Methods: A literature search was conducted using relevant keywords in online databases for appropriate publications through July 2023. Random effects model was used to calculate combined effect sizes (ESs) and 95% confidence intervals (CIs) to investigate relationship between hypothyroidism or hyperthyroidism and CRC risk.
Results: Totally, we included 13 studies in the current systematic review and meta-analysis, with a total sample size of 33,557,450 individuals and 25,363 cases of CRC. Pooling 13 effect sizes revealed no significant association between hypothyroidism and risk of CRC (combined effect size: 1.13, 95% CI 0.87-1.48, P = 0.343). There was also no significant association between hyperthyroidism and risk of CRC (combined effect size: 1.09, 95% CI 0.75-1.57, P = 0.638). Additionally, there were significant associations between hypothyroidism and risk of CRC in the Far Eastern studies, between hyperthyroidism and risk of CRC in the Middle East, along with small sample size studies.
Conclusions: This meta-analysis did not reveal any association between hypothyroidism or hyperthyroidism and risk of CRC.
Trial registration: PROSPERO CRD42022331089.
Keywords: Colorectal cancer; Hyperthyroidism; Hypothyroidism; Meta-analysis; Thyroid hormones.
© 2023. The Author(s), under exclusive licence to Springer Science+Business Media, LLC, part of Springer Nature.