Thyroid dysfunction following therapeutic external radiation to head and neck cancer.

AIM The aim of the present study was to evaluate changes in thyroid function in patients with head and neck cancer treated with external beam radiotherapy (EBRT). MATERIALS AND METHODS This prospective study was conducted on ninety patients with non-thyroid head and neck cancer who were referred to the department of radiotherapy. Thyroid function tests were conducted before, midway during and after EBRT, with follow up at monthly intervals up to 6 months after the completion of therapy. RESULTS Serum T3 and T4 levels were decreased at completion of EBRT and remained so after 6 months follow up. However, serum TSH levels did not significantly vary. CONCLUSION EBRT to the neck region for treatment of head and neck cancer induces hypothyroidism and therefore utmost care must be taken to exclude the thyroid from radiation beams without sparing the tumor as far as possible. The clinical protocol in such cases should include monitoring of T3, T4 and TSH levels during and after the EBRT.