Challenges and pitfalls in the management of endocrine toxicities from immune checkpoint inhibitors: a case presentation of synchronous thyrotoxicosis and primary adrenal insufficiency in a melanoma patient.

Background: Immune checkpoint inhibitors have revolutionized the therapeutic approach to several solid tumors, becoming the standard of care for cancer treatment in different disease settings. Despite the fact that these agents are better tolerated than conventional chemotherapy, their use is associated with a specific toxicity profile, so-called immune-related adverse events (irAEs), that can involve several organs. Endocrine irAEs are among the most frequent toxicities (around 10 to 16%) and include hypophysitis, thyroid disorders, adrenalitis, and diabetes mellitus. Some of them may be life-threatening if not promptly recognized (such as diabetic ketoacidosis and acute adrenal crisis).

Case presentation: A 55-year-old woman with a personal history of euthyroid Hashimoto's thyroiditis was diagnosed with a metastatic melanoma, BRAF wild type. Under treatment with anti-PD-1 pembrolizumab, she developed thyrotoxicosis followed by hypothyroidism due to destructive thyroiditis and concurrent primary adrenal insufficiency due to adrenalitis.

Conclusions: The simultaneous occurrence of adrenal and thyroid autoimmune diseases, resembling autoimmune polyendocrine syndrome type 2, may occur as a rare but serious side effect of ICI treatment. It often presents with abrupt onset and rapid evolution towards polyglandular insufficiency. Physicians should be aware of the potential association of two or more endocrine disorders and careful monitoring of endocrine function is needed during ICI therapy.