Background: Hypothyroidism is one of the late side effects seen after curative radiotherapy in the head and neck region encompassing part or whole of the thyroid gland. Still thyroid function tests are not a part of routine follow up of head – neck cancer patients treated with radiotherapy with or without surgery and / or chemotherapy. Aim of this study was to to find out the incidence of hypothyroidism in head – neck cancer patients treated with radiotherapy with or without chemotherapy and influence of concomitant chemotherapy. Materials and Methods: Of the 112 patients, 57 (50.8%) were planned to receive radiotherapy alone, 42 (37.5%) to receive neo-adjuvant chemotherapy with Cisplatin and 5-FU and the rest 13 (11.6%) patients to receive concurrent chemo-radiation. Thyroid function tests were done at the beginning of treatment, at six weeks after completion of radiotherapy and thereafter at six weeks’ interval for two years. Results: After 24 months follow up, overall incidence of clinical hypothyroidism of our reported patients was 31.03% and of sub-clinical hypothyroidism was 37.93%. Conclusion: As a significant number of patients develop hypothyroidism following radiotherapy to the neck, thyroid function tests should be included in the routine follow up protocol of such patients.

Keywords: Hypothyroidism, head and neck cancer, radiotherapy, thyroid function tests.