Approved research

Thyroid Dysfunction and Women's Cancer Risk

Lay summary

Epidemiological studies have suggested a possible role of thyroid hormones in carcinogenesis, especially for hormone-dependent cancers, which is consistent with known biological pathways. They nevertheless had insufficient clinical information and/or sample sizes to inform on the effect of thyroid dysfunction on the natural history of the tumours. The proposed research aims at investigating the association between thyroid dysfunction (hyperthyroidism, hypothyroidism), which is mainly diagnosed in females, and women?s cancer risk, primarily of breast, ovarian and thyroid cancers. We will investigate cancer incidence, mortality and survival, and estimate risks by histological and molecular tumour type and treatment modalities of thyroid dysfunction. Based on a large-scale prospective epidemiological study with unselected follow-up and detailed medical information, the proposed research will provide detailed and statistically robust results on women?s cancer risks associated with thyroid dysfunction. Those results will contribute to define cancer prevention strategies and support recommendations for the management of thyroid dysfunction. Analyses investigating various stages of the disease progression will also help understanding the underlying biological mechanisms and identifying etiologic factors of particular tumour subtypes, especially for those with relatively low prevalence, such as ovarian cancers, which require very large sample sizes. The study will compare incidence and mortality rates of/from breast, ovarian, thyroid cancers and other tumour sites between women who reported a thyroid dysfunction (hyperthyroidism or hypothyroidism) during the verbal interview at baseline and those who did not. We will investigate whether the risks vary according to histological and molecular tumour subtypes and thyroid dysfunction treatment modalities (e.g. surgery, radioactive iodine). The possible modifying effects of age, reproductive factors, use of exogenous hormones, lifestyle factors, personal medical history and familial cancer history will also be investigated. All women who completed the touchscreen questionnaire and answered the verbal interview, i. e. approximatively 205,000 individuals, will be included.