Evaluation of the relationship between thyroid dysfunction and breast cancer according to menopausal status

Backround: Breast cancer is the most common cancer and the leading cause of death among women in the world and in Turkey. Due to its increasing incidence in Turkey and worldwide, it is important to identify possible risk factors. The thyroid and breast are both hormonally regulated by the hypothalamus-pituitary-gland axis. Determining the relationship between thyroid dysfunctions and breast cancer is important in terms of risk analysis and preventive studies. However, the effect of hypothyroidism and hyperthyroidism on breast cancer risk and the menopausal relationship have not yet been elucidated. Aim: The aim of this study was to compare thyroid function test results of breast cancer patients according to menopausal status and to evaluate the effect on breast cancer risk. Methods: Our study included female patients who were admitted to the General Surgery Clinic of Ankara Bilkent City Hospital between February 2019 and October 2023 and diagnosed with breast cancer. Patients whose primary diagnosis was not made in our hospital and who presented with recurrence, male patients and patients whose systemic information could not be accessed were excluded from the study. Demographic information such as age, gender, postoperative pathology, diagnostic biopsy pathologic evaluation and thyroid function test (sT4, sT3 and TSH) results in the preoperative blood table were retrospectively evaluated in the data system of Ankara Bilkent City Hospital. The 1469 patients included in the study were divided into two groups as premenopausal and postmenopausal. Thyroid function test results were classified as euthyroidism, hyperthyroidism and hypothyroidism. Thyroid function tests of premenopausal and postmenopausal groups were classified and both groups were evaluated in terms of possible relationship Results:İncluded in the study, 532 (36.2%) patients were diagnosed in premenopausal period and 937 (63.8%) patients were diagnosed in postmenopausal period. The mean age of the patients was 56.43 years. Hypothyroidism was diagnosed in 16.7% and hyperthyroidism in 2.2% of the evaluated patients. 1191 patients (81.1%) were euthyroid. The mean TSH value was 2.04 mUI/ml, sT3 value was 3.01 pg/ml, sT4 value was 1.23 ng/dl. When the relationship between clinicopathological data and menopausal status was evaluated, the mean sT3 value was 3.1 pg/dl, sT4 value was 1.1 ng/dl and TSH value was 1.5 mIU/ml in premenopausal women. These values were evaluated as sT4 value 1,1 ng/dl, sT3 value 3 pg/dl, TSH value 1,6 mIU/ml in postmenopausal women. There was no statistically significant relationship between TSH values and menopausal status (p=0.332). 71.5% of hypothyroid and 75% of hyperthyroid patients were postmenopausal. In the regression analysis between hypothyroidism and hyperthyroidism, when we accepted euthyroid patients as the reference group, the probability of being hypothyroid was not higher in the postmenopausal group with an accuracy rate of 73.5%. No relationship was found between hyperthyroidism and postmenopausal period Conclusion: In our study, we observed an association between thyroid dysfunction and breast cancer, especially in postmenopausal women with hypothyroidism. Since our study data are based on retrospective examinations, the effect on disease course and prognosis cannot be evaluated. Therefore, prospective studies are needed to evaluate the effect of thyroid dysfunctions on prognosis and disease course in premenopausal and postmenopausal women and to follow up hypothyroid and hyperthyroid patients in terms of breast cancer risk. Keywords: Breast cancer, thyroid dysfunction, menopause, hypothyroidism, hyperthyroidism