Radiation-induced Hypothyroidism in Head and Neck Malignancy

Background and Objective: Hypothyroidism is a known consequence of the external beam radiotherapy to the neck encompassing the thyroid gland for over 40 years. The aim of this studywas to find out the incidence of hypothyroidism in patients with head and neck cancer treated withradiotherapy, when radiation portals included whole of the thyroid gland.Materials and Methods: This prospective non-randomized study was conducted from December2004 to February 2006. In this regard, 39 patients with head and neck malignancies referred to radiation oncology center of Hamedan whom treated with the external beam radiotherapy, whoseradiation portals included the whole of the thyroid gland. Thyroid function tests were done at thebeginning of treatment, one month, three months, six months, and one year after the completion of radiotherapy.Results: Out of 39 patients, two were excluded from the study as they had history of hypothyroidbefore the initiation of treatment. The next two were excluded from data analysis because they didnot undergo regular follow-up. Of the patients attending the follow-up clinic, 31% were found tohave sub-clinical hypothyroidism (TSH>4.5 mU/l) during a year. Conclusion: Since a significant number of patients developed hypothyroidism followingradiotherapy on the neck, thyroid function tests should be included in the routine follow-up protocol of such patients. Certain questions have emerged from this study, which need a large randomized study to find out the answers.

Keywords:

Hypothyroidism , Thyroid function tests , Cancer of Head and neck