Grave's disease induced by radiotherapy for nasopharyngeal carcinoma: A case report and review of the literature.

Radiotherapy is an effective treatment for nasopharyngeal carcinoma (NPC). A number of thyroid dysfunctions are induced by damage resulting from the relatively high doses of radiation administered to the thyroid and pituitary gland during radiotherapy. Hypothyroidism constitutes the most frequent type of thyroid dysfunction induced by NPC radiotherapy, while hyperthyroidism, particularly Grave's disease, is extremely rare. The present study describes the case of a 40-year-old male who presented with Grave's disease 2 years after receiving radiotherapy for the treatment of NPC. The patient exhibited swelling of the eyes, an increased appetite, decreased levels of thyroid-stimulating hormone, increased levels of triiodothyronine (T3) and thyroxine (T4) demonstrated by the examination of thyroid function and enlargement of the bilateral intraocular rectus revealed by CT scan. The patient's symptoms were ameliorated following treatment with propylthiouracil and propranolol for 1 month, and the levels of T3 and T4 were restored to normal. The pathophysiological mechanism of radiotherapy-induced hyperthyroidism has yet to be elucidated. Hyperthyroidism is often neglected as several of its clinical manifestations are similar to other complications observed during and following cancer treatment. Therefore, it is necessary to monitor thyroid function following head and neck radiotherapy.