Nothing Great Comes Without Its Risks: A Rare Case of Pembrolizumab-Induced Hypophysitis

Pembrolizumab is an immune checkpoint inhibitor that targets the programmed cell death protein 1 and enhances immune activity against cancer cells. This has emerged as a powerful tool in the treatment of cancer in patients with severe metastatic disease. Despite this, immune checkpoint inhibitors are associated with many immune-related adverse effects. Reported endocrinopathies include thyroid dysfunction, insulin-deficient diabetes mellitus, primary adrenal insufficiency, and hypophysitis. Hypophysitis is more commonly associated with cytotoxic T-lymphocyte associated antigen 4 inhibitors like ipilimumab and rarely with pembrolizumab. A high clinical suspicion is needed to pursue a diagnosis of immune checkpoint inhibitorinduced hypophysitis, and prompt diagnosis is of immense importance due to the potentially life-threatening nature of endocrinopathies. We present a case of a 64-year-old Caucasian male individual undergoing treatment with pembrolizumab for undifferentiated lung carcinoma who subsequently developed hypophysitis.