SUN-573 Rapid Progression of New Onset Diabetes after starting Tepezza for Thyroid Eye Disease

Abstract Disclosure: S. Kalik: None. S. Htoo: None. A. Busta: None. Background: Tepezza (teprotumumab) is an insulin-like growth factor-1 receptor inhibitor indicated for the treatment of thyroid eye disease (TED) caused by Graves ophthalmopathy and Hashimoto's thyroiditis. While the most common side effects are nausea, diarrhea and muscle spasms, severe hyperglycemia has been reported more frequently in 10-30% of cases. We present a case of rapidly worsening glycemic control and new onset diabetes after treatment with Tepezza. Case: A 66-year-old female with past medical history of Prediabetes (Hgb a1c 5.8% in September 2023), Multinodular Goiter status post right hemithyroidectomy (secondary to large nodules), Hashimoto’s, and Thyroid Eye Disease, presents to establish care in the outpatient endocrine office in October of 2023. Labs showed TSH: 4.46 uIU/mL (Reference Range (RR): 0.27 - 4.20 uIU/mL), free T4: 1.1 ng/dL (RR: 0.9-1.8 ng/dL), thyroid peroxidase antibody: 368.0 IU/mL (RR: <=34.9 IU/mL), and thyroid receptor antibody: 2.12 IU/mL (RR: 0.00-1.75 IU/mL). Hgba1c had increased to 6.0%. Levothyroxine dose was increased to 100mcg and lifestyle changes were recommended for prediabetes. Around this time, she was following ophthalmology for thyroid eye disease. She had bilateral lid retraction, worsening of horizontal diplopia with blurry vision, and severe keratoconjunctivitis. Tepezza infusion was initiated every 3 weeks for worsening TED in September of 2023. She completed Tepezza treatment by January of 2024. During endocrine follow up visit, her repeat Hgb a1c was 9.7% with blood glucose ranging between 400-500. She reported increasing fatigue, polyuria and dizziness. C-peptide level was 8.0 ng/mL (RR: 1.1-4.4) and glutamic acid decarboxylase antibody was negative. Rise of blood glucose levels and Hgba1c likely due to inhibitor effect on insulin receptors by Tepezza. She was started on basal bolus insulin, provided free style libre continuous glucose monitor and followed very closely by endocrine team. A month after initiation of insulin, Hgb a1c was 9.3%. Glimepiride 1mg once a day was added to her regimen. Four months after completing Tepezza, her Hgba1c was 6.5% and insulin requirements were decreasing. One year after completing Tepezza, her Hgb a1c was 5.5%. Insulin was discontinued and she was maintained on oral agent. Conclusion: Hyperglycemia is a known side effect of Tepezza but the incidence of new-onset diabetes and risk of diabetic keto-acidosis is unknown and needs to be studied. Patients with pre-diabetes that are started on Tepezza infusions need to be closely monitored for development of diabetes so that appropriate therapy can be initiated. Once infusions are completed, patients need to be monitored for rapid improvement in diabetes and de-escalation of treatment. Presentation: Sunday, July 13, 2025