Immune Checkpoint Inhibitor-Induced Thyroidal, Pancreatic, and Pituitary Dysfunction: Diagnostic Challenges in a Cancer Patient

Immune checkpoint inhibitors (ICPIs)-induced endocrine immune-related adverse events (irAEs) are common, can appear concurrently, and can be overlooked due to their nonspecific presentation overlapping with cancer-related symptoms. We describe the case of a 47-year-old woman with metastatic colorectal cancer treated with combined ICPI therapy. She presented thyrotoxicosis right after starting therapy, evolving into overt primary hypothyroidism, after two months, followed by abrupt-onset diabetes mellitus and hypophysisits-related secondary adrenal insufficiency and central hypothyroidism, six months after starting ICPIs. This case illustrates the complexity of diagnosing and managing overlapping endocrine irAEs, and the importance of high clinical suspicion. Clinical manifestations were attributed to the cancer and diabetes diagnosis, delaying recognition of adrenal insufficiency. Central hypothyroidism was initially interpreted as iatrogenic thyrotoxicosis. Glucocorticoid supplementation worsened diabetes management. Clinical and biochemical follow-up is essential in patients with ICPIs. Prompt recognition is essential to avoid life-threatening complications and ensure optimal long-term management.