Thyroid dysfunction in patients treated with radiotherapy for neck.

Purpose: The aim of the present study was to retrospectively evaluate the early and late changes in thyroid dysfunction after radiation therapy for head and neck cancer either with or without surgery.

Patients And Methods: Sixty-three patients receiving neck irradiation including the thyroid gland were recruited in the study. Thirty-six patients had undergone either a functional or radical neck dissection, and radiotherapy was the primary treatment in 27 patients.

Results: Of 63 patients, 24 (38%) were diagnosed with hypothyroidism (HT), 8 (12.7%) with clinical HT, and 16 (25.4%) with subclinical HT. The median time to the development of clinical HT was 15 months (range, 0-36 months) and subclinical HT was 3 months (range, 0-24 months). Eleven (17.5%) of the patients were diagnosed with subclinical hyperthyroidism. The median time to the development of the subclinical hyperthyroidism was 0 months (completion of radiation therapy) (range, 0-3 months). Univariate analyses of age, smoking history, neck RT dose, clinical stage, concurrent chemotherapy, and surgery failed to identify a clinically relevant risk factor for HT. Univariate analysis of clinical HT revealed that the elevated pre-radiation therapy thyroid-stimulating hormone level was significant factor (P = 0.021).

Conclusion: HT associated with head and neck irradiation. We recommend that thyroid function should be evaluated periodically in patients who have undergone neck radiation.