Immune checkpoint inhibitors and endocrine side effects, a narrative review

Immune checkpoint inhibitors (ICPIs) are novel drugs in the field of oncology however carry the risk of immune-related dermatologic, gastrointestinal, and endocrine side effects which can be fatal. These new innovative immunoregulatory drugs have intertwined the fields of oncology and endocrinology. CTLA-4 and PD-1 are co-inhibitory receptors on T cells that turn the T cell 'off' when binding to receptors on APCs. Tumor cells can also carry receptors for CTLA- and PD-1. By rendering T cells inactive, tumor cells can evade immune attack. Antibodies that bind to CTLA-4 and PD-1 lead to T cell activation and destruction of both tumor and normal host cells. ICPIs have been used in a variety of malignancies including melanoma, kidney cancer, and non-small cell lung cancer. A unique underrecognized side effect of the autoimmune response is hypophysitis leading to central adrenal insufficiency which can be fatal. Additional immune-related adverse events (irAEs) include hypothyroidism, hyperthyroidism, diabetes, and hypoparathyroidism.