A Rare Case of Ipilimumab-induced Reversible Hypophysitis and Permanent Primary Hypothyroidism

Ipilimumab is a monoclonal antibody targeting the cytotoxic T-lymphocyte antigen-4 receptor, which was originally approved for the treatment of metastatic melanoma. It is the first immune checkpoint inhibitor to enter clinical practice. Immune toxicity due to ipilimumab causing colitis, hepatitis, and dermatitis are well-described in literature. We report a case of hypophysitis resolving with corticosteroid treatment, following which the patient developed long-term primary thyroid impairment. This highlights the importance of vigilance for rarer immune-related toxicities as clinical utilization of ipilimumab becomes more widespread.