Abstract:Objective To study the hormone levels and clinicopathological characteristics of patients with thyroid cancer and breast cancer, and to explore the possible relationship between the two cancers. Methods Clinical data of 82 cases of thyroid cancer with breast cancer (combined cancer group) patients and 86 cases of simple thyroid cancer (thyroid cancer group) patients in The First Affiliated Hospital of Xinjiang Medical University from January 2010 to December 2022 were collected. According to whether the BMI was greater than 24, patients in combined cancer group were divided into overweight combined cancer group (n=37) and normal combined cancer group (n=45), and patients in thyroid cancer group were divided into overweight thyroid cancer group (n=44) and normal thyroid cancer group (n=42). The general characteristics, pathological characteristics, thyroid hormone and endocrine hormone levels of the two groups, and pathological features of different BMI subgroups were compared. Results There was no significant difference in age, BMI and menstrual status between the two groups (P＞0.05). However, the tumor diameter of patients in overweight combined cancer group was (0.65±0.33) cm, which was significantly smaller than that of patients in overweight thyroid cancer group ［(1.06±0.97) cm］, and the difference was statistically significant (t=2.452, P=0.018). The proportion of patients with previous reproductive history in the combined cancer group was significantly higher〖LM〗 than that in the thyroid cancer group (93.90% vs 80.23%, χ²=6.892, P=0.009). The levels of thyroxine, estriol and progesterone were higher in the combined cancer group than those in the thyroid cancer group, and the differences were statistically significant (P＜0.05). The level of testosterone in the combined cancer group was significantly lower than that in the thyroid cancer group ［0.77(0.48,1.02) nmol/L vs 0.88(0.68,1.21) nmol/L,z=3.008, P=0.003］. Conclusion Patients with thyroid cancer combined with breast cancer have higher serum thyroxine, progesterone and estritol and lower testosterone levels on clinical biochemical markers compared with patients with thyroid cancer alone. Although no correlation was found between BMI and clinicopathologic features, the pathological features of overweight patients with breast cancer and thyroid cancer showed smaller tumor diameter. Therefore, health education and disease screening for obese patients should be strengthened clinically.