Secondary Adrenal Insufficiency as an Immune-Related Adverse Event of Pembrolizumab Therapy

Pembrolizumab is an immune checkpoint inhibitor that blocks the PD1 receptor and is currently used in the treatment of a vast variety of malignancies. Despite adrenal insufficiency already being documented as a rare but potential side effect, its diagnosis is usually delayed due to its vague presentation, increasing the risk of deleterious outcomes. We present a case of secondary adrenal insufficiency while on pembrolizumab, in which the diagnosis was delayed due to a nonspecific clinical picture. This case highlights the importance of maintaining a high index of suspicion for endocrine dysfunction in patients treated with immune checkpoint inhibitors, as early recognition and appropriate intervention are paramount to preventing serious complications in these patients.