Highlighting such cases can improve early recognition and management.<h4>Patient concerns</h4>A 56-year-old man with esophageal cancer developed fatigue, polyuria, polydipsia, dizziness, and severe hyponatremia after treatment with tislelizumab, a PD-1 inhibitor.<h4>Diagnoses</h4>Laboratory evaluation revealed new-onset autoimmune diabetes, hypothyroidism, and secondary adrenal insufficiency. The gene discussed is PDCD1; the disease is hypothyroidism.