Thyroid function after radiation and surgery for head and neck cancer

Preoperative radiation followed by surgical excision is accepted therapy for head and neck cancer. The effects of these modalities on thyroid function were evaluated in a prospective study. Sixty-one patients were given cobalt 60 radiation. Results showed that 41 patients (67%) were euthyroid, 12 patients (20%) were clinically and chemically hypothyroid, and 8 patients (13%) had transient loss of thyroid reserve. Permanent hypothyroidism occurred frequently in patients with hemithyroidectomy, but rarely in those treated with radiation alone. Onset of hypothyroidism was zero to six months, with transient loss of thyroid reserve occurring up to 18 months. This constitutes the initial report of an ongoing systematic study of thyroid function in such patients. The high incidence of hypothyroidism indicates a need for careful periodic evaluation.