(14.07) Severe thyrotoxicosis with "impending storm" requiring multiple hospitalizations in a patient with papillary thyroid carcinoma status post-thyroidectomy treated with adjuvant radioactive iodine therapy: A case of post-radiation thyroiditis.

Introduction : Thyrotoxicosis is a clinical syndrome characterized by an excess thyroid hormone, leading to various signs and symptoms including excessive sweating, neck pain, anxiety, hypertension, tachycardia, and diarrhea. Destructive thyroiditis is a condition in which preformed thyroid hormone from inflamed and damaged thyroid follicles is released. Causes include autoimmune thyroid disease (Hashimoto thyroiditis), postpartum thyroiditis, medication-induced, infectious (viral or bacterial), and radiation-induced thyroiditis. Radiation thyroiditis occurs in 1% or less of cases receiving radioactive iodine (RAI) in Graves’ disease patients and is of rare occurrence in post thyroidectomy patients. We present a unique case of severe thyroiditis with impending storm in patient with Papillary thyroid carcinoma s/p total thyroidectomy who was treated with high dose of RAI ablation as an adjuvant therapy.

Case(s) Description : A 42-year-old male with a past medical history of Papillary thyroid carcinoma status post total thyroidectomy with residual neck disease who received RAI ablation with 210 mCi as adjuvant treatment. Patient presented to hospital with severe neck swelling and pain with difficulty swallowing that started immediately after treatment and continued to worsen. He reported significant anxiety, photophobia, headache, and tremors. Before diagnosis of thyroiditis was made, patient had two hospitalizations for these symptoms that were treated symptomatically. Physical examination revealed a tender anterior neck mass, fine tremors, hypertension, and tachycardia with heart ranging between 110-130s. Initial laboratory tests demonstrated TSH: < 0.01 mIU/L (Reference Range: 0.4-4.0 mIU/L); Free T4: > 7.77 ng/dL (Reference Range: 0.9-1.7 ng/dL); Free T3: 23.60 pg/mL (Reference Range: 2.3-4.2 pg/mL); Total T3: 3.76 ng/mL (Reference Range: 0.8-2.0 ng/mL); Thyroglobulin: 18361.7 ng/ml. Thyroid ultrasound showed remnant thyroid tissue with. Based on clinical findings, laboratory results, and thyroid hormone tests, the patient was diagnosed with severe thyrotoxicosis due to post-radiation thyroiditis, a rare complication of RAI therapy in thyroid cancer patients who underwent total thyroidectomy. Patient was treated with: Propranolol, prednisone taper, and supportive measures. The combination of beta-blockers and antithyroid medications gradually improved the patient's thyrotoxicosis, and his symptoms resolved over the period of several days.

Discussion : This case highlights the rare but severe complication of thyrotoxicosis following adjuvant RAI treatment in thyroid cancer patients with residual disease. It emphasizes the importance of pre- radiation surgical management and debulking of local neck disease that may include revision surgeries for residual disease and neck dissections especially in advanced and local metastatic cases, given the treatment doses for cancer treatment are significantly higher than doses used for Graves’ disease. Close monitoring and timely intervention to manage this condition effectively is the key.