Iatrogenic Pituitary Shutdown: A Rare Adverse Event of Programmed Cell Death-Ligand 1 Inhibitor

Immune checkpoint inhibitors (ICIs) are one of the novel treatment strategies for malignancies, and their wide use has led to the emergence of immune-related adverse events (irAEs). Most of them have been reported in patients taking cytotoxic T lymphocyte-associated protein 4 inhibitors and are rarely reported among those taking programmed cell death-ligand protein 1 inhibitors. Here is a 74-year-old man who underwent treatment with atezolizumab for 33 weeks for hepatocellular carcinoma before presenting with chronic symptoms and laboratory results consistent with central adrenal insufficiency. Brain imaging did not show a possible culprit. He was incidentally found to have low thyrotropin (TSH) and low thyroxine prior to his presentation and began replacement with no further workup prior. We advocate keeping a low threshold for the diagnosis of adrenal insufficiency among patients taking ICIs and monitoring their pituitary hormones on a regular basis. Also, it is crucial to rule out pituitary hormonal deficiency among patients with central hypothyroidism prior to initiating replacement.