Immune Checkpoint Inhibitor-Induced Endocrine Dysfunction: Early Detection of Symptoms and Timely Intervention.

Immune checkpoint inhibitors (ICI) target immune regulatory pathways to enhance antitumor responses. Although these agents improve survival, they can cause immune-related adverse events (irAEs). Hypophysitis is a recognized irAE-particularly with CTLA-4 inhibitors-but this case is notable for occurring in an elderly patient receiving combination therapy and presenting with nonspecific symptoms that mimicked cancer-related fatigue and treatment side effects. We report a 76-year-old woman on ICI therapy who developed intractable back pain, nausea, and severe hyponatremia, ultimately diagnosed with ICI-induced hypophysitis. Her evaluation revealed multiple electrolyte abnormalities, secondary adrenal insufficiency, and pituitary enlargement on magnetic resonance imaging (MRI), necessitating urgent fluid resuscitation and corticosteroid replacement. As use of ICIs expands across malignancies, understanding the side effect profile and atypical or subtle presentations is essential in providing prompt diagnosis and treatment of sequelae that can mimic autoimmune diseases. It underscores diagnostic complexity in real-world settings and the need for heightened awareness of adverse endocrine events, especially in older patients and those receiving sequential or combination regimens. Careful monitoring of irAEs allows for irAEs risk mitigation and improves patient tolerability in continuing ICI cancer treatment. Clinicians should maintain a high index of suspicion and implement appropriate monitoring protocols for early detection.