She remained on propranolol for treatment of her symptoms, but PTU was discontinued. Eight days later, the patient received Fraxinellone 10 mCi of I-131 as an oral tablet for thyroid ablation. concentrations at diagnosis should receive prolonged pretreatment with anti-thyroid drugs. While such an approach may Fraxinellone reduce the efficacy of I-131 ablation, it can also reduce and hopefully eliminate the risk of post-ablative thyroid storm. strong class=”kwd-title” MeSH Keywords: Graves Disease, Hyperthyroidism, Thyroid Storm, Pediatrics, Iodine Radioisotopes Background Graves disease results from the inappropriate production of thyroid-stimulating immunoglobulins (TSI), binding of TSI to thyroid-stimulating hormone receptors, and the resultant secretion of Fraxinellone excess thyroid hormone. A growing number of pediatric endocrinologists treat Graves disease with radioactive iodine (RAI) therapy due to the typically definitive nature of Iodine-131 (I-131). Given the published benefits and perceived low risks of RAI when compared to surgery or long-term anti-thyroid medication, the trend towards therapy with RAI is likely to continue. However, RAI is not without significant risk. Herein, we report a case of thyroid storm presenting 1 day after RAI in an 11-year-old with recent-onset Graves disease. Case Report An 11-year-old Caucasian girl was evaluated in an outside emergency department after a 4-day history of tachycardia, shortness of breath, wheezing, and tachypnea. She was treated for presumed pneumonia and started on antibiotics. After 24 hours of persistent tachycardia (160C190 beats per minute) she was transferred to our academic institution for further treatment and evaluation. Review of systems revealed no heat intolerance, diaphoresis, tremor, weight loss, difficulty sleeping, or fatigue, but she did report recent onset of diarrhea and decreased oral intake. Notably, the patient felt that her tachycardia had begun only 4 days prior to admission. Upon her arrival, thyroid function tests were performed and revealed a markedly elevated free T4 ( 6 ng/dL), elevated T3 ( 500 ng/dL), and suppressed TSH ( 0.01 mIU/L). Review of her records revealed that a TSH measured by her primary care doctor 3 months before admission was suppressed (TSH 0.08 mIU/L). Pertinent findings on her initial physical exam included blood pressure (BP) 136/67, heart rate (HR) 132, temperature 36.6C, height 144 cm (20th percentile), and weight 36 kg (20th percentile). There was no proptosis or exophthalmos. She had mild flattening of the face and micrognathia. Her thyroid was diffusely enlarged, smooth, and firm with no palpable nodules. A thyroid bruit was not appreciated. She had slight tremor of her hands at rest. Given her thyroid function studies and physical exam findings, she was presumptively diagnosed with Graves disease and was prescribed propranolol 10 mg 4 times daily (1.25 mg/kg/day) and propylthiouracil (PTU) 50 mg 3 times daily (4.7 mg/kg/day). Notably, this case occurred prior to the Food and Drug Administrations (FDA) release of a black box warning for PTU secondary to liver toxicity. Thyroid autoantibody assays were ordered and she was discharged from the hospital the following day with instructions to follow up with Pediatric Endocrinology. Thyroid autoantibody testing confirmed the diagnosis of Graves disease. Thyroid binding inhibiting immunoglobulin assay (TBII) was markedly elevated at 51% (16% or less), thyroid-stimulating immunoglobulin (TSI) assay was normal at 98% (0C129%), thyroid peroxidase antibodies were elevated at 835.1 IU/mL ( 3.9), and thyroglobulin antibodies were negative ( 1:100). A thyroid uptake scan was not performed given the unequivocal laboratory values. The patient returned to the Pediatric Endocrinology clinic 4 days after hospital discharge. Fraxinellone The family noted increasing difficulty administering 2 different medications multiple times per day. As such, the relative risks and benefits of continued anti-thyroid medication versus surgery versus RAI were discussed. Because the patient and her mother eagerly sought more definitive therapy, she was referred to our radiation oncology colleagues and scheduled for RAI ablation. She remained on propranolol for treatment of her symptoms, but PTU was discontinued. Eight days later, the patient received 10 mCi of I-131 as an oral tablet for thyroid ablation. PR55-BETA Vital signs measured prior to ablation revealed temperature of 36.2C, HR 101, and BP 129/55. The following morning she reported being unusually sleepy and became increasingly unresponsive over the next 2C3 hours. She was transported to the closest emergency department.