Hypothyroidism after Radiotherapy for Head and Neck Cancer Patients

We report two cases of hypothyroidism with clinical symptoms that occurred after radiotherapy for cancer of the head and neck. The first patient underwent total laryngectomy without thyroidectomy for laryngeal cancer and partial gastrectomy for gastric cancer. Radiation of the neck was carried out postoperatively. Two years later, he developed chest pain and pericardial effusion was detected, leading to a diagnosis of myxedema due to hypothyroidism. The second patient received radiotherapy alone for laryngeal carcinoma. Two months later, a low serum sodium concentration and anemia were detected, both of which proved difficult to correct. The cause of these changes was found subsequently to be hypothyroidism. From the experience of these 2 cases, we measured thyroid function in 37 patients who had received neck radiation for head and neck cancers at our hospital over the past 10 years. In 13 of the 37 patients (35%), hypothyroidism was observed. The prevalence of hypothyroidism was higher in the 13 patients treated with both radiation and surgery, with 6 (46%) showing this condition, compared with 7 of the 24 patients (29%) who received radiation alone. The risk factor responsible for hypothyroidism was not evident from statistical analysis of these cases. We consider that thyroid function should be evaluated periodically in patients who have received neck radiotherapy, as it is often difficult to diagnose hypothyroidism from clinical symptoms.