Thyroid function in breast cancer patients before and up to two years after mastectomy

In 41 women newly diagnosed as having breast cancer the thyroid function was assessed by determination of the serum TSH, tririodothyronine (T3), reverse triiodothyronine (rT3), thyroxine (T4), T3-resin uptake and free T4-index. Blood samples were drawn before the primary treatment and at follow-up after 7-28 months. There was no significant change in any of these variables during the period of observation. Nor was there any difference between the values of the patients who developed recurrent disease and of those who did not. These results contradict previously proposed hypotheses of a progressive decrease in thyroid function after primary treatment and of a relation between the clinical course and the thyroid function in breast cancer patients.