12337 Nivolumab Induced Secondary Adrenal Insufficiency And Hypothyroidism In A Patient With Graves’ Disease: A Case Report

Abstract Disclosure: F. Sajid: None. J. Kaur: None. A. Zatsepina: None. M. Khan: None. C.A. Resta: None. Introduction: We present a case of a patient with Graves’ disease who developed concurrent secondary adrenal insufficiency (SAI) and primary hypothyroidism while undergoing treatment with nivolumab for non-small cell lung cancer (NSCLC). This case sheds light on the immune-related adverse events (irAEs) associated with immune checkpoint inhibitor (ICI) therapy. Case Presentation: A 63-year-old woman with a history of Graves’ disease and NSCLC undergoing neoadjuvant chemoimmunotherapy was admitted with hyponatremia. She was diagnosed with Graves’ disease a year before and was treated with methimazole (MMI). When she was diagnosed with Graves’ disease, her TSI was 1.64 IU/L (<0.55). Before starting nivolumab, TSH had normalized at 0.5 MCIU/mL on MMI therapy. She started nivolumab 3 months before admission. One month after starting nivolumab, her TSH was <0.01. By the time she was admitted, she had severe hypothyroidism and SAI with sodium 116 mmol/L (135-149), TSH 40.34 mIU/mL (0.39-4.08), free T4 <0.25 ng/dL (0.8-1.8), TSI 21.2 IU/L (0.00-0.55) Total Cortisol 0.4 ug/dL (6.7-27.6), AM Cortisol 0.6 ug/dL, ACTH <1.5 pg/mL (7.2-63.3), LH 75.5 IU/L (7.7-58.5), and FSH 179 IU/L (25.8-134.8). MMI was discontinued due to hypothyroidism. She was started on replacement therapy with levothyroxine and hydrocortisone. Subsequent sodium levels normalized. Discussion: Nivolumab has emerged as a promising immunotherapy for NSCLC. Our patient developed irAEs following nivolumab treatment. Notably, this case represents only the third documented case to our knowledge of both primary hypothyroidism and secondary adrenal insufficiency occurring post-nivolumab treatment. Workup for our patient revealed two irAE’s. She developed primary hypothyroidism and isolated ACTH deficiency with other pituitary function remaining normal. The pattern of thyroid profile over time was consistent with thyroiditis due to ICI therapy. TSI increased, ruling out remission from Graves’ disease. Even after discontinuing methimazole, she remained hypothyroid. Hence, in this case, ICI effectively acted as definitive therapy for her Graves’ disease. Conclusion: This case sheds light on the intricate interplay between nivolumab therapy, pre-existing autoimmune conditions such as Graves’ Disease, and the emergence of irAEs. This case underscores the importance of vigilant monitoring of serum sodium levels, and thyroid and pituitary function tests in patients undergoing immunotherapy. Presentation: 6/1/2024