Thyroid function following neck irradiation for malignant lymphoma.

Thyroid function tests for T3 resin (T3-r), serum thyroxine (T4) and serum thyroid stimulating hormone (TSH) were measured in 70 consecutive patients who had previously undergone lymphangiography and neck irradiation for malignant lymphoma. All were in remission and clinically euthyroid. The abnormalities found were: 23 (33%) patients hypothyroid by TSH, 14 (20%) with subnormal T4, and 21 (30%) with subnormal T3-r values. None of the patients were biochemically hyperthyroid. The prevalence and magnitude of abnormalities were highest during the third year after irradiation, thereafter decreasing with time.