PDCD1 and hypothyroidism: A systematic review reported that the incidences of hypothyroidism and thyrotoxicosis were 3.8% and 1.7% after treatment with an anti-CTLA4 antibody, 7.0% and 3.2% after treatment with an anti-PD-1 antibody, and 13.2% and 8.0% after treatment with anti-CTLA4 and anti-PD-1 antibodies, respectively (3, 6).