radiation-induced thyroiditis radiation-induced thyroiditis radiation-induced thyroiditis is a form of painful, acute thyroiditis resulting from radioactive therapy to treat hyperthyroidism or from radiation to treat head and neck cancer or lymphoma. it affects 1% of those who have received radioactive iodine (i-131) therapy for graves' disease, typically presenting between 5 and 10 days after the procedure. stored t3 and t4 are released as rapid destruction of thyroid tissue occurs which results in pain, tenderness, and exacerbation of hyperthyroidism.