SAT-374 Elevated Insulin-like Growth Factor -1 And Growth Hormone Levels In Patients Receiving Teprotumumab (tepezzaTm)

Abstract Disclosure: P.N. Truong: None. M.K. Shakir: None. T.D. Hoang: None. Background: Graves’ orbitopathy, also known as thyroid eye disease (TED), is an autoimmune inflammatory disorder related to the overexpression of insulin-like growth factor 1 receptor (IGF-1R). Teprotumumab, a human monoclonal antibody targets and inhibits the IGF-1R and has been first-line therapy for patients with moderate to severe TED. We present a descriptive study of IGF-1 and growth hormone (GH) levels during Teprotumumab treatment in patients with TED. Methods: A retrospective review was carried out on 19 patients (>18 years old) with a diagnosis of TED who underwent a total of 8 intravenous infusions over a 24-week period. Our goal was to assess IGF-1 and GH levels before, during, and after Teprotumumab treatment and observe for any trends. Adverse events were also assessed. Not all patients had laboratory studies consistently obtained during all phases of treatment. Results: Prior to Teprotumumab initiation, all 19 patients had normal IGF-1 levels with a range from 75 ng/mL to 242 ng/mL (age and gender matched). All 19 patients had elevated in IGF-1 levels during treatment with a range from 343 ng/mL to 1684 ng/mL. A 53-year-old male’s baseline IGF-1 level of 152 ng/mL increased to a peak of 738 ng/mL and decreased to an IGF-1 level of 137 ng/mL after 7 months of discontinuing Teprotumumab treatment . An 18-year-old female’s baseline IGF-1 level was 242 ng/mL and increased to a peak of 757 ng/mL and trended toward 345 ng/mL after 8 months. A 49-year-old male’s IGF-1 level starting treatment was 646 ng/mL and increased to 885 ng/mL, but his IGF-1 level was 168 ng/mL 3 months after the last infusion. In 2 out of 19 patients with GH levels obtained, a 30-year-old female and a 45-year-old female showed elevated GH levels with peaks of 13.7 ng/mL and 26.7 ng/mL, respectively, and had elevated IGF-1 levels of 682 ng/mL and 568 ng/mL, respectively. Significant drug related adverse events include hyperglycemia and increase in hemoglobin A1c level. Discussion: In our study, serum IGF-1 levels increased in all patients, and IGF-1 levels were normalized only after 7-8 months approximately after the last infusion of Teprotumumab. In the two patients that had elevated GH levels, it was observed that IGF-1 levels also rose in relation toward peak level. Future studies may be able to investigate this feedback regulation pathway between IGF-1 and GH. In conclusion, Teprotumumab administration can cause elevated IGF-1 and GH levels and this may persist for several months. Presentation: Saturday, July 12, 2025