Thyroid function in women with breast cancer

The thyroid function was evaluated in a study group of 226 breast cancer patients and in control groups, consisting of 125 patients with various other malignancies, 61 women with benign breast disease and 166 healthy blood donors. The mean serum concentrations of total T₃ and T₄ were significantly higher in the breast cancer group than in the controls. The mean TFI (thyroid function index), measured by two indirect techniques (T₃RU, T₄/TBG) or by direct free T₄ measurement, was also significantly higher in this group of patients than in controls. Individual values of TFI exceeding the upper limit of the normal range were related with elevated total T₄ levels and not with abnormal concentrations of total TBG. Eight women with breast cancer (3.5%) and one patient with head and neck cancer were clinically hyperthyroid. No case of overt hypothyroidism was observed. There was no relation between thyroid function and spread of the disease (TNM). The control groups, including patients with other-than-breast cancers, did not show any significant modification of the thyroid function tests. In the present study, breast cancer patients, as a group, show a thyroid dysfunction distinct from the non-specific abnormalities (low T₃ syndrome) frequently observed in patients with a variety of acute or chronic non-thyroidal illnesses.