A case of pembrolizumab-induced hypopituitarism subsequent to hypothyroidism

subsequent to hypothyroidism: A 60-year-old man was treated with pembrolizumab for recurrence of lung metastasis after surgery for hy-popharyngeal carcinoma. Three months after the first dose, severe hypothyroidism was observed. This was thought to be an immune-related adverse event （irAE） and treatment was temporarily discontinued. Levothy-roxine was started, thyroid function recovered, and pembrolizumab was restarted. Seven months after the first dose, general malaise and anorexia were observed. On the basis of the decrease in serum ACTH and cortisol levels, we diagnosed hypopituitarism as an irAE. Hydrocortisone was administered and the general condition promptly improved. Hypothyroidism induced by immune checkpoint inhibitors is a frequently observed irAE and may be secondary to hypopituitarism, as in this case.