Objective:

Recent studies indicated an association between thyroid autoimmunity and breast cancer, but the causality still needed to be proven. The aim of this study was to compare the prevelance of autoimmune thyroid diseases (ATD) between breast cancer patients and the control group. We hypothesised that breast cancer patients have a higher ATD prevalance and higher thyroglobulin gene polymorphism rates than the control group.

Materials and Methods:

The study was designed as a prospective matchedcohort investigation. Control sample size was determined according to 1:1 matching with cancer cases. The study group included 100 consecutive breast cancer patients admitted to “Marmara University Hospital”, while the control group included 100 women admitted to outpatient clinics in whom breast cancer was ruled out. Thyroid autoantibody, thyroid and sex hormone levels were measured and compared between study and control groups. In order to compare Tg gene polymorphism rates between breast cancer and control groups, although cancer tissue samples were obtained from study patients, a different control group with the same age, sex and ethnicity with the study group was constituted from the hospital’s tissue bank.

Results:

Autoimmune thyroid disease prevalances were similar between study (n=25) and control (n=18) groups. Tg gene polymorphism prevalences were also similar between the two groups. Estrogen levels were significantly higher in patients with ATD (89.75±84.4 pg/mL) when compared to those without (54.17±73.89 pg/mL).

Conclusion:

In conclusion, the prevalences of ATD and Tg polymorphism were similar between breast cancer cases and controls. As a significant finding, patients with ATD among all the cohort (with and without breast cancer) had higher serum estrogen levels when compared to those without.

Keywords: Breast cancer, autoimmune thyroiditis, thyroglobulin, genes