Pembrolizumab-induced Thyroiditis, Hypophysitis and Adrenalitis: A Case of Triple Endocrine Dysfunction

Immune checkpoint inhibitor drugs can trigger autoimmune endocrine reactions as a known side effect. Several cases of immunotherapy-induced autoimmune endocrinopathies have been described, but multiple sequential endocrine toxicities are a rare occurrence. A 39-year-old patient with metastatic melanoma started adjuvant therapy with pembrolizumab. One month later he presented with asymptomatic thyrotoxicosis and, within several weeks, overt hypothyroidism, for which he started levothyroxine therapy. Subsequently the patient developed central adrenal insufficiency due to probable hypophysitis, and steroid replacement therapy was started. Pembrolizumab therapy was then discontinued. After a few months, a full recovery of pituitary function was observed, but primary adrenal insufficiency occurred, requiring additional fludrocortisone therapy. The described clinical case is a very uncommon case of triple endocrinological toxicity from immunotherapy. The clinical and biochemical manifestations of immunotherapy-induced endocrinopathies can be variable and atypical; therefore, it is necessary to pay special attention to any clue of hormonal dysfunction.