Purpose: The relationship between breast cancer and thyroid diseases is controversial. Conflicting results have been reported in the literature. The incidence of autoimmune and non-autoimmune thyroid diseases were investigated in patients with breast cancer who had received prior therapy as compared with age-matched control individuals without breast or thyroid disease.
Patients and methods: Clinical and ultrasound evaluation of the thyroid gland, and determination of serum thyroid hormones and autoantibody levels were performed in 143 breast cancer patients and 128 healthy control individuals. Patients were classified into subgroups according to estrogen receptor (ER) and progesterone receptor (PR) status and type of oncological treatment.
Results: The mean values for serum antibodies against thyroid peroxidase (anti-TPO) were 9 IU/ml and 25 IU/ml for antithyroglobulin antibodies (anti-TGB) in breast cancer patients, and 9.5 IU/ml and 23.5 IU/ml, respectively, in the control group (p>0.05. The difference between breast cancer patients and the control group in the incidence of autoimmune and non-autoimmune thyroid diseases was not statistically significant. No significant differences between the groups according to both menopausal status and ER status were seen (p= 0.67). Also, no significant influence of hormonal therapy with tamoxifen and chemotherapy on serum levels of thyroid stimulating hormone (TSH), free thyroxin (fT4), TPO and TGB autoantibodies was proved.
Conclusion: This study demonstrated a similar incidence of thyroid enlargement and the same frequency of thyroid disturbances in patients with breast cancer and controls. No relationship was found among ER and PR status, and the presence of serum thyroid autoantibodies. Although we have been unable to demonstrate any impact of breast cancer therapy on thyroid function tests, more prolonged studies with larger number of patients may be required to demonstrate significant trends.