Association of thyroid disorders and breast cancer: a retrospective case-control study

This study investigated the association between thyroid disorders and breast cancer.

A retrospective case-control study was conducted using electronic health record data from an academic health care system. This study included 300 female patients 18 years of age and older with a diagnosis of breast cancer and 300 control individuals with no cancer history. Statistical analysis included calculation of prevalence and odds ratios for association, ꭓ2 for categorical variables, and mean (SD) and median for age.

Patients with breast cancer were, on average, 58 years old, statistically significantly older than patients without cancer (P < .001). Patients were 6 times more likely to have thyroid disorders (P < .001), including hypothyroidism (P < .001), than women who did not have cancer. Patients with triple-negative breast cancer had 4 times higher odds of being diagnosed with thyroid disorders overall (P < .001) and hypothyroidism (P < .001) compared with control individuals. Moreover, patients with estrogen receptor-positive/progesterone receptor-positive breast cancer were 15 times more likely to develop the autoimmune disorder Hashimoto thyroiditis compared with controls, which was statistically significant (P = .026).

This study highlighted a strong association between breast cancer and thyroid disorders, particularly indicating a higher prevalence of hypothyroidism among individuals with breast cancer.