Endocrine Adverse Events of Immune Checkpoint Inhibitors: A Comprehensive Review

Immune checkpoint inhibitors (ICIs) have revolutionised cancer therapy by enhancing T-cell-mediated tumour eradication. However, their use is associated with immune-related adverse events, with endocrinopathies being the most common. Thyroid dysfunction, hypophysitis, primary adrenal insufficiency (PAI), and insulin-dependent diabetes mellitus are well-documented complications. Thyroid dysfunction typically follows a biphasic course, with transient thyrotoxicosis progressing to hypothyroidism. Hypophysitis primarily affects the anterior pituitary, often leading to isolated adrenocorticotropic hormone deficiency. ICI-induced diabetes mellitus results from autoimmune β-cell destruction, frequently presenting as diabetic ketoacidosis. Primary adrenal insufficiency is rare but requires prompt recognition. Despite these endocrine toxicities, the benefits of ICIs outweigh their risks, and treatment is usually continued with appropriate hormone replacement. Early recognition and management of these endocrinopathies are crucial for optimising patient outcomes. This review summarises the incidence, pathophysiology, diagnosis, and management of ICI-associated endocrine disorders, providing essential insights for oncologists and endocrinologists.