Endocrine Abstracts

Diabetes caused by immune checkpoint inhibitors is extremely rare. A 48-year-old male patient with a diagnosis of squamous cell cancer in the external auditory canal and operated on received adjuvant radiotherapy. When relapse was seen, 6 cycles of 5-fluorouracil, carboplatin, and cetuximab were administered. The patient was admitted to the hospital with nausea, vomiting, and abdominal pain 10 days after the second cycle infusion, when pembrolizumab was started when the cranial MRI showed progression 6 months later. Serum glucose: 717 mg/dl (70–100), creatinine: 1.5 mg/dl (0.7–1.2), sodium: 132 mmol/l (136–145), potassium (K): 5.5 mmol/l (3.5–5.1), amylase 55 U/l (13–53), blood pH: 7.02 (7.35–7.45), pCO₂: 29 mmHg (35–45), HCO₃: 8 mEq/l (22–26), lactat: 1.9 mmol/l (0.5–1.6), urinalysis; ketons: ++++, glucose: ++++. Treatment was started with the diagnosis of diabetic ketoacidosis and the desired c-peptide due to possible immune checkpoint inhibitor-induced diabetes mellitus: <0.001 ng/ml, anti-insulin antibodies: 1.5 U/l (0–10), GAD antibodies: 718 IU/ml (0–10) were found. TSH required for other possible immune-related adverse events: 1.6 µIU/ml (0.2–4.2), free T4: 1 ng/dl (0.9–1.7), anti thyroid peroxidase: 11 IU/ml (0–34), anti thyroglobulin: 11 IU/ml (0–115), cortisol: 16 µg/dl (6–18), and no other immunocheckpoint-related endocrinopathy was detected. The patient who responded to ketasidosis treatment was discharged with insulin therapy. The treatment was not stopped because the patient’s response to pembrolizumab treatment was good. The side effects of these drugs, whose immune checkpoint inhibitors act by blocking the inhibitory mechanisms on the immune system, are also autoimmune events that occur as a result of excessive immune response. There were no other more common autoimmune side effects in our patient, who was diagnosed with autoimmune diabetes. While using these drugs, patients should be followed up carefully for other possible side effects, as well as for autoimmune diabetes.