A Case of Metastatic Renal Cell Carcinoma Developing Isolated Adrenocorticotropic Hormone (ACTH) Deficiency During Nivolumab Therapy

We report a case of isolated adrenocorticotropic hormone (ACTH) deficiency that developed after nivolumab therapy for metastatic renal cell carcinoma involving the pancreas and thyroid. The patient presented with nonspecific symptoms that improved promptly after discontinuation of nivolumab and initiation of hydrocortisone replacement therapy. Despite permanently requiring glucocorticoid supplementation, the patient has maintained a durable partial response for more than four years after cessation of nivolumab. This case highlights the importance of early recognition of immune-related endocrinopathies and demonstrates that long-term tumor control may be achieved even after discontinuation of immune checkpoint inhibitors.