Endocrine Abstracts

Introduction: Immunotherapy has demonstrated a key role in the current individualized treatment of multiple neoplasms, with adverse events related to the endocrine. Thyroid dysfunction is the most frequent reported endocrine event during treatment with pembrolizumab, being autoimmune diabetes an extremely rare adverse effect.

Case Report: We present a case of a 72-year-old man with a progressing urothelial bladder carcinoma (stage IIIB), under treatment with pembrolizumab since 2018. He had the diagnosis of primary hypothyroidism four months after starting the treatment, no personal or family history of diabetes mellitus, and his usual fasting plasma glucose levels were 102-113 mg/dl in the last six months. He was admitted in 2022 due to abdominal pain, anorexia, polydipsia, polyuria, nausea and vomiting with one week of evolution after performing contrast-enhanced imaging, with criteria for severe diabetic ketoacidosis (DKA) (pH 7.18, HCO3 2.9 mEq/l, glucose 695 mg/dl, ketonemia 7.3 mmol/l). He was medicated with prednisolone 20 mg/day three days before admission, due to suspected contrast hypersensitivity reaction. During hospitalization, he underwent fluid therapy with KCl supplementation and intravenous insulin infusion, having transitioned to a basal-bolus scheme after DKA resolution, with progressive glycemic stabilization. Further investigation revealed undetectable levels of C-peptide (0.07 ng/ml), HbA1c 9.2% and positive islets autoimmunity (positive anti-IA2 antibodies), which allowed the diagnosis of autoimmune diabetes. The drug was transiently suspended, and the patient resumed treatment after glycemic profile optimization under insulin therapy.

Conclusion: This clinical case highlights the importance of clinical suspicion and glycemic monitoring in addition to thyroid function, as an integral part of treatment protocols in patients on pembrolizumab and other immune checkpoint inhibitors. In the presence of autoimmune diabetes, the need for long-term insulin therapy is invariably necessary, with the possibility of resuming the drug after adequate glycemic stabilization.