Hypothyroidism after radiotherapy for laryngeal cancer

Purpose: To investigate the incidence of hypothyroidism after radiotherapy of laryngeal cancer, including the possible factors that could predict the onset of hypothyroidism. Materials and methods: We report this study on patients treated by radiothe rapy as part of the treatment for laryngeal cancer in the Department of Onc ology in Eastern Finland. Sixty-five males and seven females were treated w ith radiotherapy between 1974-1995. Thyroid function was determined by measuring serum thyroid stimulating horm one, and serum free thyroxine (FT4). The studied risk factors for hypothyro idism included age, treatment modalities, radiation dose and energy, height of the radiation field, and follow-up time. Results: Hypothyroidism was detected in 17 (24%) of the 72 patients. Hypoth yroidism was clinically unsuspected in all but one patient. Hypothyroidism was more common, if the height of the radiation field was greater than or e qual to7 cm, or the patient had been operated. Hypothyroidism was less comm on if less than a half of the thyroid bed was irradiated. Conclusion: The detection of hypothyroidism clinically is difficult, and th e rate of hypothyroidism warrants routine assessment of thyroid function af ter irradiation of laryngeal cancer. (C) 2000 Elsevier Science Ireland Ltd. All rights reserved.