The presence of thyroid disease may lead to an increased risk of breast disease. Both thyroid and breast diseases are endocrine-related. If thyroid system disease occurs, the level of thyroid hormones in the body increases, and the levels of TSH, T4 and T3 hormones in the body also change, which can easily lead to disruption of hormone secretion in the body, especially estrogen. If thyroid system disorders occur, the release of hormones in the body will be disrupted and estrogen will increase, causing breast cells in the body to be affected, resulting in breast hyperplasia and even differentiation of breast cells in the body. In severe cases, this can cause breast cancer. There may be a relationship between the thyroid and the breast, and once thyroid disease occurs, the breast should be examined.