Thyroid Dysfunction Following Management of Non-thyroid Head and Neck Cancers

Head and neck cancers are one of the commonest malignancies in India. Majority of cases of head and neck malignancy undergo chemoradiation with or without surgery. Thyroid bears the brunt in terms of either excision or the gland tends to get irradiated and fibrosed. In either scenario the functionality of gland is lost leading to hypothyroidism and other clinical manifestations. It tends to get subclinical and goes unnoticed. To identify the occurrence of clinical and subclinical hypothyroidism among head and neck cancer patients receiving radiation to the neck and to justify routine use of thyroid function tests during follow up. It was a prospective non randomized control study of 100 patients of head and neck cancer receiving radiotherapy for duration of 1 year. Thyroid stimulating hormone and T3 and T4 estimations were done at baseline and at 3 and 9 months following radiotherapy. Out of 100 patients, 72 (72%) were males and 28 (28%) were females. All the patients received radiation to the neck to a dose of >30 Gy. 35 patients received concurrent chemotherapy. 11 patients were found to have subclinical hypothyroidism while 32 patients developed significant clinical hypothyroidism (P value of 0.001). Thus a total of 43 patients developed radiation induced hypothyroidism. 20 of the 32 patients who developed clinical hypothyroidism were in the age group of 41-50 years. 11 of 32 patients who developed clinical hypothyroidism received chemoradiation while rest 21 received radiotherapy alone. Mean period for developing radiation induced hypothyroidism was 4.5 months. Hypothyrodism (clinical or subclinical) is an under recognised morbidity of external radiation to the neck which is seen following a minimum dose of 30 Gy to the neck. Recognising hypothyroidism (clinical or subclinical) early and treating it prevents thyroid dysfunction related complications. Hence, thyroid function tests should be made routine during follow up in all patients undergoing radiotherapy.