Hypothyroidism is most frequent with an estimated incidence of 2.5–3.8% (anti-CTLA4), 3.9–8.5% (anti-PD1/PDL1), and 10.2–16.4% (combination treatment), typically occurring at a median time of 8–12 weeks post ICI initiation (56). The gene discussed is CTLA4; the disease is hypothyroidism.