The relationship between breast cancer and thyroid autoimmune disorders in southeast Iran: A case-control study.

Objective. To better understand the role of thyroid hormones in regulating the growth of breast epithelial cells and the estrogen-like effects of these hormones, the present study was conducted to investigate the relationship between breast cancer and thyroid autoimmune disorders in southeast Iran women. Methods. In this case-control study, in the case group, all newly diagnosed breast cancer pa-tients referred to the oncology clinics in Zahedan city in years 2021‒2022 were studied. The num-ber of participants in each group was represented by 40 breast cancer patients. The control group was represented by women without breast cancer. The sampling method was simple or available using the nonprobability method. The presence or absence of thyroid dysfunction was checked using thyroid-stimulating hormone (TSH), free thyroxin (FT4), free triiodothyronine (FT3), anti-thyroid peroxidase (TPO), and anti-thyroglobulin (Tg) tests. Results. The mean age of participants was 47±11 years. The risk of subclinical hyperthyroid-ism was higher in subjects with breast cancer and about 8 times higher than in the healthy ones (OR=8.27). According to the value of OR=1, the risk of developing autoimmune thyroid disease was the same in individuals with breast cancer as in healthy individuals. The odds ratio of hypothy-roidism could not be calculated because the value in the control group was zero. Conclusion. The results of this study show that there are abnormal characteristics of the thy-roid gland in breast cancer patients compared to the control group. The incidence of subclinical hyperthyroidism was significantly increased in the breast cancer patients. However, there was no difference in the incidence of autoimmune thyroid disease between the two groups.