SUN-018 Panhypopituitarism Secondary to Immunotherapy With Nivolumab and Ipilimumab

Abstract Disclosure: E. Abidor: None. B. George: None. R. Dankar: None. C. Kaspar: None. J. Zaidan: None. Introduction: Immune checkpoint inhibitors such as nivolumab and ipilimumab have revolutionized cancer treatment but are associated with immune-related adverse events, including endocrine dysfunction. Panhypopituitarism represents a significant complication that requires prompt recognition and management. Case Report: We present the case of a 77-year-old male with BRAF-V600E negative metastatic melanoma treated with nivolumab and ipilimumab (completed four cycles, last cycle three days prior to presentation) who developed generalized weakness, nausea, and intermittent confusion over three weeks. He presented to the emergency department with hypotension (98/50 mmHg) and hyponatremia (Na 123 mEq/L). Initial workup for sepsis, including blood and urine cultures, was negative. Despite fluid resuscitation and withholding his home medication chlorthalidone, his hyponatremia only minimally improved (Na 126 mEq/L after 72 hours). Endocrine evaluation revealed low morning cortisol (1.20 μg/dL), low ACTH (<5 pg/mL), low TSH (0.167 mIU/mL), and low free T4 (0.5 ng/dL), consistent with secondary adrenal insufficiency and central hypothyroidism. Corticosteroid and thyroid hormone replacement were initiated, resulting in clinical improvement. Immunotherapy was discontinued at the recommendation of the patient's oncologist. Post-discharge, further evaluation revealed low total testosterone (1 ng/dL), low free testosterone (0.1 pg/mL), low LH (0.3 mIU/mL), with a normal FSH (4.0 mIU/mL), and a low IGF-1 (23 ng/mL; Z-score -2.6 SD), suggesting secondary hypogonadism and growth hormone deficiency. Conclusion: This case highlights the potential for combined nivolumab and ipilimumab to induce panhypopituitarism, and it underscores the importance of considering pituitary dysfunction in patients receiving immunotherapy who present with non-specific symptoms. Early recognition and hormone replacement are crucial for optimal management. Presentation: Sunday, July 13, 2025