Drugs/interventions: No therapy is assigned, patients starting immune checkpoint inhibitors (ICIs) provide blood samples to measure endocrine autoantibodies. ICIs referenced are monoclonal antibodies: anti-CTLA-4 (ipilimumab, tremelimumab), anti-PD-1 (cemiplimab, dostarlimab, pembrolizumab, nivolumab), and anti-PD-L1 (atezolizumab, avelumab, durvalumab). Mechanism: these mAbs block inhibitory checkpoints (CTLA-4, PD-1/PD-L1), releasing brakes on T cells to boost anti-tumor cytotoxic responses. Targets/cells/pathways: T cells via CTLA-4 and PD-1 signaling, APC–T cell priming, tumor immune evasion pathways. Study measures endocrine autoimmunity affecting thyroid, pituitary, adrenal, and pancreatic beta cells via biomarkers: aTg, aTPO, TRAb/TSI, pituitary Ab, adrenal Ab, anti-GAD. Goal: associate baseline antibodies with endocrine irAEs and oncologic outcomes.