Abstract:

Objective  To systematically evaluate the correlation between hyperthyroidism and the risk of breast cancer，to provide the theoretical basis for etiological study and primary prevention of breast cancer. Methods  Data of case-control studies and cohort studies of hyperthyroidism and breast cancer were collected by searching 8 electronic databases from inception to April 2018. The Newcastle-Ottawa quality scale（NOS） was used to evaluate the quality of inclusion study and a Meta-analysis was conducted by RevMan 5.3 software. Results  Finally 17 studies were included in the meta-analysis，which including 10 case-control studies and 7 cohort studies，with a total of 66，116 cases. The concrete results were as follows：⑴case-control study：the results of unadjusted OR showed that hyperthyroidism couldn't increase the risk of breast cancer（OR=1.25，95%CI：0.92-1.70，P=0.150）；the results of adjusted OR showed that hyperthyroidism could increase the risk of breast cancer（OR=1.11，95%CI：1.03-1.19），P=0.004）.⑵cohort study：unadjusted OR and adjusted OR combined results showed that hyperthyroidism could increase the risk of breast cancer （unadjusted OR=1.17，95%CI：1.07-1.27，P<0.001；adjusted OR=1.11，95%CI：1.07-1.15，P<0.001）. Conclusions Hyperthyroidism may increase the risk of breast cancer. However，the relationship between and breast cancer risk in different regions is not exactly the same.

Key words: Breast neoplasms, Hyperthyroidism, Risk, Meta-analysis